Osmotic agents Glucose Glucose has been the standard osmotic agent in PD solu- tions, but h as several limitations. PD equipment design A variety of designs of PD equipment have been devel- oped, with the ai ms of reducing peritonitis rates and CHAPTER 13.4 Peritoneal dialysis 509 Table 13.4.1 Typical composition of peritoneal \202 uid Biocompatibility of PD \202 uid Biocompatibility of PD \202 uid can be de \201 ned as the ability to perform its role without inducing adverse effects in the patient \200\223 p articularly change in peritoneal membrane, and also immune cell dysfunction. Bioincompatibi lity of PD \202 uids is due to the toxicity of: \200 \200 \200 \200 \200 Solute Concentration Electrolyte Sodium Potassium Calcium Magnesium Chloride 132 \200\2233 mmol/L 0 ( \200\2232) mmol/L 1.0 \200\2231.75 mmol/L 0.25 \200\2230.75 mmol/L 95 \200\223102 mmol/L high glucose concentrations; high osmolality; acid pH; lactate buffer; glucose degradation products (GDPs) produced from heat sterilization of glucose solutions. Buffer 35 \200\22340 mmol/L Lactate or Lactate/bicarbonate or Bicarbonate 25/10 \200\22315 mmol/L Solutions have been developed to try to overcome these factors. Icodextrin and amino acid \202 uids have some biocompatible features. A variety of newer glucose-containing solution s are available which are low in GDPs, have neutral pH and use bicarbonate or a mixture of bicarbonate and lactate as a buffer. Neutral pH reduces symptoms of infusion pain. Long-ter m clinical bene \201 ts of these \202 uids are currently under investigation. 34 \200\22339 mmol/L Osmotic agent 1.36 \200\2233.86 g/dL Glucose (anhydrous) or Amino acids or Icodextrin 1.1 g/dL 7.5 g/dL It is absorbed from the peritoneum relatively quickly (espe- cially with higher peritoneal membrane transportation status). This leads to loss of its osmotic effectiveness and reduce d or negative ultra \201 ltration on longer dwell times. Absorbed glucose results in metab olic complications such as hyperglycemia, hyperinsulinemia, hyperlipidemia and weight gain. Exposure of the peritoneal membrane to high concentra- tions of dialyzate glucose adversel y affects peritoneal membrane structure and function. Peritoneal membrane function testing Peritoneal membrane function differs between individua ls. Variability occurs in the rate of movement of small solutes between the patient and the dialyzate. More rapid movement equates to the presence of a greater number of small pores, or effective vascular surface area (higher trans- porters). Peritoneal equilibration test (PET) This is the common test of peritoneal membrane function . Two litres of 2.27% glucose dialyzate is infused into the peritoneal cavity for a 4 h per iod. Dialyzate samples are taken after infusion, and at 2 and 4 h and analyzed for creatini ne and glucose. A blood sample is taken at 2 h. Graphs are plotted of the ratio of dialyzat e to plasma (D:P) creatinine concentrations and the ratio of dialyzate glucose concentratio ns at sample time to that at time zero. Comparison with standard curves derived from popula tion studies allows classi \201 cation of the patient \200\231s solute trans- porter statu s as: \200 \200 \200 \200 Amino acids Amino acid dialyzate solutions contain amino acids instead of glucose as the os motic agent. An exchange of 1.1% amino acid solution achieves equivalent ultrafiltration to 1.36% glucose solution and typically provides 20 \200\22325% of the patient \200\231s dai ly nitro- gen requirements by absorption of amino acids from the dialyzate. Usually only on e exchange is used per day as more can result in the development of uremia and acidosis. Icodextrin Icodextrin is a large glucose polymer and acts as a colloid osmotic agent (simil ar to large molecules such as albu- min). It acts at the small intercellular pores and is o nly slowly lost from the peritoneal cavity. Unlike glucose, it produces gradual and sustain ed ultra \201 l- tration over long dwell periods and may be more effective in achieving ul tra \201 ltration in higher transporters. It is used for a single long dwell daily \200 \223overnight in CAPD or the day dwell in APD. Being glucose free, it may avoid the adverse peritoneal membrane and metabolic effects of glucose. Some icodextrin metabolites are abso rbed. This leads to a small fall in serum sodium and increase in osmolality or osmolar gap in plasma, which is not of clinical signi \201 cance. These absorbed metabolites can cause overestimation of blood glucose by some patient glucometers (with risk of undiagnosed hypo glycemia). low; low average; high average; high. Increasing transportation state is associated with more rapid rise in dialyzate creatinine and fall in dialyzate glucose con- centrations over time. The net ultra \201 ltration at 4 h is also useful, with a value <100 mL suggesting ultra \201 ltration failure. Standardized permeability analysis (SPA) The test is similar to the PET, but: \200 uses 3 .86% glucose dialyzate; \200 has an additional sample of dialyzate extracted at 1 h; \200 dialyzate samples also analyzed for sodium. G. WOODROW 510 SPA classi \201 es transportation status in the same way as PET. The fall in dialyzate sod ium at 1 h (sodium dipping) re \202 ects aquaporin function. Net UF <400 mL at 4 h with 3. 86% glucose is a more robust de \201 nition of ultra \201 ltration failure than that with PET. Thus patients with low ultra \201 ltration will develop sodium overload and hypertension. Sodium sieving Part of the ultra \201 ltration induced by glucose is water passage without accompanying solutes, through the ultra- small pores. This water transportation without so dium is termed sodium sieving. The measured fall in dialyzate sodium at 1 h in the SPA re \202 ects sodium sieving and aquaporin function. Over a 4 h dwell, sodium concentrations wi ll equilibrate between dialyzate and plasma by diffusion. With hypertonic glucose exchanges and very short dwell times (e.g. in APD), sodium removal may be low relative to ultra \201 ltration volume (i.e. sodium sieving greater), as there is less time for dialyzate sod ium concentration to equili- brate with plasma by diffusion. Fluid balance management Maintaining normal \202 uid balance is a primary role of PD. Hyd ration depends on a balance of intake and input. Determining correct dry weight is a dif \201 cult and imprecise process. Clinical assessment can be insensitive to signi \201 cant \202 uid imbalance. Fluid overload is associated with adverse cardiovascular effects suc h as hypertension, and development of left ven- tricular hypertrophy and dysfunction. Hyper tension in the absence of other evidence of \202 uid overload may be due to \202 uid ex cess and respond to \202 uid removal, but care is necessary to avoid dehydration and loss of residual renal function in patients who still pass urine. Appropriate individualized in structions should be given to patients with regard to their \202 uid and sodium intake al low- ances. Water and sodium loss occur through dialysis and also residual renal function. Urine volume (but not clearance) may be enhanced by prescription of high doses of loop diur etics. Assessment of \202 uid overload in PD Fluid overload has many potential causes and carefu l sys- tematic assessment is essential to make the correct diag- nosis and institute correc t treatment. The majority of cases are not due to primary peritoneal membrane failure. Excessive \202 uid intake Fluid overload from excess \202 uid intake can result from: \200 thirst due to high sodium intake or hyperglycemia in poorly controlled diabetes; inadequate education or instruction about intake; nonconcordance. \200 Ultra \201 ltration with PD Dialyzate \202 uid removal is dependent on: \200 \200 \200 It is important to recognize these as they are reversible. the osmotic agent; duration of dwell; peritoneal membrane transportation status. Loss of residual renal function Loss of residual urine output may cause \202 uid retentio n in otherwise stable subjects. It should be recognized and treated by: \200 \200 \200 Ultra \201 ltration may be increased by: \200 \200 reduction of \202 uid intake allowance; altered dialysis prescription to increase \202 uid removal; high dose loop diuretics to increase urinary water and sodium excretion. using more hypertonic glucose dialyzate; shorter dwell times (and thus less time for loss o f glu- cose and its osmotic effect). It is essential to avoid dwells with negative ultra \201 ltration. This is most likely to occur in the long day dwell of APD or the overnight dwell of CAPD and can be managed by: \200 adding additional exchanges to shorten dwell times; \200 using more hypertonic gluc ose; \200 use of solutions containing icodextrin (whose sustained ultra \201 ltration pr o \201 le is better-suited to long dwell peri- ods than glucose). Catheter dysfunction and other mechanical problems Mechanical problems such as catheter mal function and peritoneal \202 uid leaks also lead to inadequate \202 uid removal despite a healthy peritoneal membrane. PD prescription errors PD prescription errors commonly result in inadequate \202 uid remo val and \202 uid retention. Problems include inade- quate strength glucose dwells or too long cycles. The long dwell is a particular problem (overnight in CAPD or day in APD) as th e long time period allows greatest loss of osmotic agent. There is clear evidence that for the long dwell, icodextrin can improve \202 uid balance compared with glucose. Ultra \201 ltration failure Ultra \201 ltration failure is an important cause of PD tech- nique failure that may require transfer to HD. It may be speci \201 cally de \201 ned as net \202 uid removal below a de \201 ned value during peritoneal membrane function test ing: \200 \200 Ultra \201 ltration failure Where initial assessment fails to reveal a reversible cause, a ssessment of peritoneal membrane function can aid in con \201 rming and classifying ultra \201 ltration failure. If \202 uid removal in the peritoneal function test is satisfac- tory, this suggests that the patient does not have ultra \201 ltra- tion failure and furth er search for other reversible causes should be made. Where achieved ultra \201 ltration i s low, this suggests ultra \201 l- tration failure and the transportation characteristics determined by the test can suggest the mechanism. < 100 mL/4 h in PET test with 2.27% glucose; < 400 mL/4 h in SPA test with 3.86% glucose. Sodium removal During the course of a dwell, sodium concentrations between dialyzate and pl asma will tend to equilibrate by diffusion. Peritoneal sodium removal is however largely ac hieved by sodium accompanying water removal by ultra \201 ltration, with little sodium los s occurring by diffusion. CHAPTER 13.4 Peritoneal dialysis 511 Higher transporter status The commonest cause of ultra \201 ltration failure is a high per itoneal membrane transportation state, which results in rapid loss of osmotic agent from th e peritoneal cavity for small solutes such as glucose and amino acids. This com- monly deve lops after time on PD and episodes of peritoni- tis. Improvement of ultra \201 ltration re quires PD with: \200 \200 Protein catabolism due to an in \202 ammatory state in uremia. Malnutrition, in \202 amma tion and atherosclerosis (MIA) syn- drome describes wasting as part of an in \202 ammatory state associated with cardiovascular disease, and is not respon- sive to increasing dietar y nutrient intake and may be seen in patients on PD. Causes of malnutrition speci \201 c to PD In PD, glucose absorption and abdominal fullness may lead to appetite suppression. Delayed gastric emptying may occur (especially in patien ts with diabetic autonomic neuropathy). Protein and amino acids are lost in dialyzate, vary ing between 5 and 15 g/day (increased in peritonitis). Dietary protein requirements are up to 1.2 g/kg body weight in PD (higher than healthy individuals in part to balance dialyzate losses). Many patients have an intake as low as 0.8 g/kg but maintain stable state in the absence of additional nutri- tional stresses (but are at risk of decompensation with any ad ded insult). An energy intake of 35 kcal/kg is recommended. greater glucose concentrations; shorter exchanges. Higher transportation patients may have most effective ultra \201 l- tration with the shor t dwell times of APD regimes. Icodextrin achieves its ultra \201 ltration effect at the sm all pores, which are relatively impermeable to it, and there- fore in contrast to glucose i t may actually be more effective in patients with higher transportation status. Low transportation status Ultra \201 ltration failure with a low transportation state is r are and a serious situation, resulting in both poor \202 uid manage- ment and solute clea rance. It implies major damage or disruption to the intraperito- neal space. This pattern c an, however, also result from the coexistence of a low transportation status with a reversi ble mechanical problem and this combination should be excluded. Management of malnutrition Optimizing dialytic clearances. Correcting reversible factors. D ietetic supervision of intake. Nutritional supplementation. High average and low average transporters Ultra \201 ltration failure with high average or low average trans- port state may result in situations where there is enhanced \202 uid absorption from the peritoneal cavity (increased lym- phatic or abdominal wall \202 uid a bsorption) aquaporin de \201 - ciency or the presence of a mechanical complication. PD catheter-related infections Exit-site infection An acute exit-site infection is de \201 ned as the presence of purulent discharge from the exit site which may be associ- ated wit h: \200 \200 \200 \200 Management of UF failure: Where the primary problem is reduced ultra \201 ltration capacit y of the membrane, strategies include: \200 \200 erythema; edema; granulation tissue; tenderness. Use of hypertonic glucose exchanges. Shortened dwell time: overnight APD cycles; additional daytime CAPD dwells; shortening long dwell times by additi onal overnight exchange in CAPD (by automated exchange device); manual exchange during day in APD. Exit-site infections can lead to development of peritonitis. They may be resistant or relap sing and may require cathe- ter removal for cure. A variety of organisms may cause exit sit e infec- tions. Staphylococcus aureus and Pseudomonas spp are common and most likely to lea d to peritonitis or catheter loss. A chronic exit-site infection may develop from an untrea ted or inadequately treated exit site infection. Use of icodextrin for long dwell of CAPD or APD. Nutrition Malnutrition occurs when there is inadequate nutrient intake or nutrient imbalanc e leading to adverse conse- quences for health. There is a high prevalence of malnutrition in patients on PD (as also occurs in hemodialysis). Malnutrition is a potent adverse progno stic marker for patient survival. Many factors lead to malnutrition and wasting in patients on PD. Some are common to all patients with advanced renal failure, whereas others are spe ci \201 c to PD. Investigations The responsible organism should be identi \201 ed by culture of the exit si te. A positive culture without clinical features of infection is due to bacterial colonizat ion and does not require antibi- otic treatment. Management Management of the infected exit site includes local meas- ures including regular cleaning of the exit site and removal of exuberant granulation tissue. Hypertonic saline c leaning has also been suggested for aggressive infections. Antibiotic treatment is essentia l for exit-site infections. Causes of malnutrition in renal failure Reduced nutrient intake due to uremic anorexia. Coe xistent acute and chronic medical conditions. Metabolic factors: \200 \200 \200 acidosis; insulin resistance; abnormalities of growth hormone metabolism. G. WOODROW 512 Antibiotic treatment should be guided by microbiological results, but empirical treatment i s often initiated before they are available. Initial treatment should be active against Sta phylococcus aureus. Pseudomonas spp. should also be covered if the patient has had previous exit-site infections with this organism. Duration of therapy should be for a minimum of 2 weeks, with further extension if resolution is slow or incomplete. Catheter removal is requ ired for persistent exit-site infec- tion, or where there is an associated peritonitis. Rev ision of the catheter tunnel and shaving of the external cuff of a two-cuff catheter have b een advocated for persistent exit-site infections in an attempt to preserve the catheter. S imultanous removal of the infected catheter and inser- tion of a new catheter on the other side of the abdomen can be performed, with ongoing antibiotic treatment, in the absence of peritonitis. Other rarer routes of infection leading to PD peritonitis include bloodborne infection and ascending infection from the female genital tract. Prevention of peritonitis Intensive training of patients by specialist PD nurses in per- fo rming dialysis procedures and aseptic technique signi \201 - cantly reduces the risk of pe ritonitis. Regular follow-up assessment of the patient and reassess- ment in those sufferin g infections are advised. PD systems may also in \202 uence the rate of peritonitis. There is some evidence suggesting a lower rate of perito- nitis in patients on APD compared to C APD. However, the evidence is inconsistent and APD systems involving \200\230spik- ing \200\231 of the dialyzate bags may be associated with an increased peritonitis risk. The in troduction of CAPD systems incorporating a \200\230dou- ble-bag \200\231 design with \202 ushing of the connection and drain- age of dialyzate before \201 lling with fresh di alyzate had a major effect on reducing PD peritonitis rates. These should be systems of cho ice for patients receiving CAPD. Guidelines suggest that a peritonitis rate of <1 episode o f peritonitis per 18 patient-months of PD treatment should be obtained. Tunnel infection A tunnel infection is de \201 ned by the presence of signs of in \202 am mation along the track of the subcutaneous portion of the catheter and may be associated wi th purulent dis- charge from the exit site. Investigations are the same as those for an exi t-site infec- tion and USS may be used to con \201 rm the presence of a localized collecti on associated with the catheter. Antibiotic treatment is essential for tunnel infections an d empirical treatment is the same as for exit-site infec- tions. Tunnel infections are more likely to fail to respond to anti- biotic treatment and there is a high chance that the PD catheter will need to be removed. Diagnosis of PD peritonitis Clinical presentation of peritonitis is most commonly with clou dy dialysis \202 uid associated with abdominal pain. Rarely PD peritonitis presents as ab dominal pain with ini- tially clear dialyzate which subsequently becomes cloudy. Peritoniti s should not therefore be excluded in the PD patient with abdominal pain if the initial dia lysis \202 uid sam- ple is clear, though alternative causes for abdominal pain should be sought. Dialysis \202 uid samples are obtained to determine \202 uid white cell count a nd for microbiological testing. A dialyzate sample with >100 white cells/ L (of which \211 50% are neutrophils) indicates peritoneal in \202 ammation, with PD peritonitis being the most likely cause. There are concerns that \202 uid from short dwells may pro- vide a false-negative result in the presence of infection due to a low white cell count. If in d oubt, dialyzate can be instilled for a period of 1 \200\2232 h and the resulting \202 uid white cell count is reliable in con- \201 rming or excluding the presence of peritonitis . The Gram stain is often negative, but may be useful in dem- onstrating the presence of a fungal infection. Fluid should ideally be sent for culture before commencing antibiotic the rapy. Correct culture techniques are essential to maximize the chance of obtaining a positi ve bacterial culture. Centrifugation of 50 mL of dialyzate for 15 min, with resus- pension of the sediment in 3 \200\2235 mL of saline and subse- quent inoculation onto culture mediu m has been advocated as the most effective method. Alternatively 5 \200\22310 mL of dialyza te can be inoculated directly into blood culture bottles. It is recommended that microbiolo gical investigations of peritonitis should have a culture-negative rate of <20%. PD peritonitis Peritonitis is one of the most important complications of PD. Despite improv ements in \200\230connectology \200\231, dialysis proce- dures and prophylaxis, peritoniti s is an important cause of acute and long-term PD technique failure, morbidity, hospi- tali zation and occasionally death. Route of infection Peritonitis can arise through varying routes of infection into the perit oneal cavity. Passage of organisms may occur via the catheter lumen after contamination at the connection procedure. Coagulase-negative staphylococcal peritonitis commonly occurs via this route. The incidence of this infection may be particularly affected by improvements i n \200\230connec- tology \200\231 and the performance of dialysis procedures by the patien t. Pericatheter passage of bacteria from the skin along the catheter tunnel may also occur, often associated with a catheter tunnel infection. Organisms commonly causing peritonitis via this route include Staphylococcus aureus and Pseudomonas aeruginosa. Enteric organisms may cause peritonitis by passage from the bowel lumen into the peritoneal cavity. This may be associated with the presence of diverticular disease of the large bowel, or through tran smural migration of organisms. Rarely PD peritonitis results from acute surgical abdominal conditions such as visceral perforation. Management of PD peritonitis Antibiotic therapy should be initiated as soon as peritonitis is suspected and after collecting samples for culture. CHAPTER 13.4 Peritoneal dialysis 513 Initial treatment is commenced before culture results become available and should cover bot h Gram-positive and Gram-negative organisms (including Pseudomonas aer- uginosa). Debate ha s raged over the most appropriate initial antibi- otic regime, particularly regarding the r elative bene \201 ts (convenience and ef \201 cacy) and risks (antibiotic resistance) of empirical use of vancomycin. The 2005 International Society of Peritoneal Dialysis (ISPD) g uidelines suggest center-speci \201 c protocols based on the pattern of organisms and sens itivities observed in individ- ual practices. Gram-positive organisms should be covered by vancomy- cin or a cephalosporin. Gram-negative organisms should be covered by an aminoglyco side, third-generation cepha- losporin (or quinolone if there is a high proportion of sen- sitive organisms in local results). Antibiotics are commonly given intraperitoneally either by: \200 Some units advocate the use of a urokinase \202 ush of the PD catheter if there is recurr ent peritonitis in an attempt to strip the catheter of bio \201 lm. Staphylococcus aureus This organism often causes severe infection and arises from catheter infection or touch contamination of the dialysis procedure. Catheter-related infection may require catheter removal to allow resolution. Streptococcal and enterococcal infections These are treated with intraperitoneal ampicillli n. An aminoglycoside may be added for synergistic effect in enterococcal infections. Vancom ycin-resistant infections have been reported. Pseudomonas infection This is typically severe and often associated with catheter infection . Treatment with a combination of two antipseudomonal antibiotics is recommended. Other Gra m-negative infections are also often serious, with worse outcomes than Gram-positive infect ions. Treatment is with an appropriate antibiotic chosen on the basis of sensitivities (typ ically a cephalosporin or aminogly- coside). continuous dosing with the antibiotic present in all infused dialysis \202 uid; intermitt ent dosing where the antibiotic is only adminis- tered for the long dwell period. It is important to con \201 rm the stability of the antibiotic in the dialysis \202 uid being used. Increasing data are becoming available for intraperitoneal antibiotic dosing re gimes. Antibiotics may also be administered orally or intrave- nously. Treatment of periton itis is more complicated on APD due to the intermittent nature of the treatment. However, i nfections can be effectively treated while maintaining patients on their usual APD dialysis regime without swap- ping to CAPD. Intermittent dosing regimes are available for a number of antibiotics, where they may be administered once daily into the long day dwell of APD pa tients or overnight in CAPD. Vancomycin is slowly cleared and may be administered less freq uently, with doses given once every 3 \200\2237 days as deter- mined by blood vancomycin le vels. Many episodes of peritonitis are accompanied by only mild symptoms and the patient ma y be treated as an outpatient. In more severe cases treatment may require hospitaliza- tion . The minimum recommended duration of antibiotic treat- ment for PD peritonitis is 2 weeks, extended to 3 weeks for more serious or slowly responding infections. Heparin may be added to dialyzate when large amounts of \201 brin are present, to maintain \202 ow and prev ent catheter occlusion. Culture-negative peritonitis This results from: \200 \200 \200 fastidious organisms; previous antibacterial therapy; limitations of culture techniques. If clinical improvement is occurring, initial antibiotic ther- apy can be continued, though continuation of Gram-nega- tive cover may not be necessary. If not responding, culture for unusual organisms may be performed, but catheter removal is usually required. Polymicrobial infection Polymicrobial infection with multiple Gram-negative bacte- ria, esp ecially when with anerobic organisms, is often asso- ciated with underlying intra-abdominal pathology. Surgical and radiological assessment is essential. Antibiotic therapy should in clude appropriate Gram-nega- tive cover and metronidazole. Infection with multiple Gram-pos itive organisms carries a better prognosis and frequently responds to antibiotic therapy. Fungal peritonitis Fungal peritonitis carries a signi \201 cant risk of mortality. Cathete r removal is considered mandatory. Initial treatment may be with a combination of amphoter- icin B and \202 ucytosine until identi \201 cation of the organism and sensitivities. Speci \201 c infections Once culture and sensitivity results become available, sub- sequen t antibiotic therapy should be adjusted appropri- ately according to advice from microbiolo gy (local practice may vary). Mycobacterial peritonitis Mycobacterial peritonitis, due to Mycobacterium tuberculo- sis or nontuberculosis mycobacterium, is a rare cause of PD peritonitis. Diagnosis may be made on repeated \202 uid culture in sus- pected cases. Laparotomy and peritoneal biopsy may be needed. Coagulase-negative Staphylococcus aureus This infection is often clinically mild, but may l ead to relaps- ing infection due to catheter bio \201 lm formation. The organism commonly exhibits methicillin resistance and antibiotic choice is between vancomycin and \201 rst- gen- eration cephalosporins. G. WOODROW 514 Treatment is as for extrapulmonary mycobacterial disease with adjustment of regime as appro priate for the use and safety of drugs in renal failure. The necessity for catheter removal is uncertain. Episodes of infection are also associated with long- term changes in peritoneal membrane fu nction leading to increased transportation state and eventual ultra \201 ltration failure. Peritonitis may contribute to the development of encapsu- lating peritoneal sclerosis. Adh esion formation after infection may prevent the fur- ther use of the peritoneum for dialysi s. Severe sepsis can occasionally be fatal. Complicated infections Refractory peritonitis: \200 an infection failing to clear after 5 days of appropriate antibiotics. Relapsing peritonitis: \200 PD infections and antibiotic prophylaxis Some antibacterial prophylactic regimes reduce the inci- dence of exit-site infections. Mupirocin daily at the exit site or nasally for 5 \200\2237 days per month (either in all patients, or those carrying S. aureus on screening nasal swabs) has been shown to reduce the risk of exit-site infections, but there is concer n about the risk of development of mupirocin resistance. If applied to the exit site, mupir ocin cream rather than ointment should be used, as the latter may damage some catheters. Ex it-site application of gentamicin cream has also been demonstrated to reduce exit-site infe ction rates. Antibiotic prophylaxis may be indicated to prevent devel- opment of peritoniti s in the PD patient undergoing invasive procedures. Dialysis \202 uid should be drained o ut before any procedures involving the abdomen or pelvis. an infection within 4 weeks of completing antibiotics with the same organism or sterile cul ture. Recurrent peritonitis: \200 an infection within 4 weeks of completing antibiotics with a different organism. Repeat peritonitis: \200 an infection after 4 weeks of completing antibiotics but with the same organism. Catheter removal is required for: \200 \200 \200 refractory and relapsing peritonitis; fungal peritonitis; nonresponding mycobacterial infec tion. In relapsing infection the catheter may be removed and simultaneously replaced after resolu tion of the second infection and with appropriate ongoing antibiotic cover. Surgical causes of peritonitis in PD It is important to consider the possibility that an un der- lying surgical pathology may present with apparent PD peritonitis. Causes include: \200 \200 \200 \200 Noninfective causes of cloudy dialyzate Eosinophilic peritonitis Eosinophilic peritonitis i s characterized by cloudy dialyzate with a high proportion of eosinophils on differential w hite cell count in dialyzate. This is most commonly seen early after commencing PD and may re \202 ect an allergic reaction to components of dialysis \202 uid, bags or tubing or P D catheter. It often settles spontaneously on continuing dialysis but rarely corticosteroid s or antihistamines have been used. Other causes include exposure to intraperitoneal antibi otics. acute appendicitis; diverticulitis; perforated viscus (peptic ulcer or diverticular disease ); acute pancreatitis. Surgical disease should be considered particularly when: \200 \200 \200 \200 the patient is disproportionately unwell; systemic signs of sepsis; suggestive clinical his tory; multiple enteric/anerobic agents on PD \202 uid culture. When investigating suspect ed acute pancreatitis, serum amylase may be misleadingly low in patients receiving ico- dex trin dialyzate due to interference of icodextrin metab- olites with the amylase assay. Mali gnancy may also present as cloudy dialyzate and may be identi \201 ed by radiological imag ing or presence of malig- nant cells on cytology of spent dialyzate. Chylous ascites Chylous ascites produces creamy white dialyzate with a very high triglyceri de content. Arises from blockage or damage to intra-abdominal lym- phatics. Can be associat ed with malignancy involving the lymphat- ics, including lymphoma. May occur intermittently , related to fat-containing meals. Complications of PD peritonitis PD peritonitis may result in malnutrition due to: \200 \200 \200 Icodextrin Cases of sterile peritonitis have occurred in patients treated with batches of i codextrin \202 uid, attributed to con- tamination with high peptidoglycan concentrations. increased peritoneal protein loss; reduced nutrient intake; acute catabolism. There may be a temporary reduction in ultra \201 ltration during peritonitis due to increa sed peritoneal vascu- larity increasing the transportation status of the membrane as a resu lt of peritoneal in \202 ammation. This may be man- aged by: \200 \200 \200 Mechanical complications of PD Catheter drainage problems Drainage problems may occur becau se of: \200 \200 \200 \200 constipation; malposition/migration of the catheter; abdominal adhesions; catheter occlusio n (e.g. \201 brin, and omental wrapping). shortening dialysis exchanges; hypertonic \202 uids; use of icodextrin for long dwells. CHAPTER 13.4 Peritoneal dialysis 515 Management Management of \202 uid leaks is a period of rest from PD to allow the leak to heal. PD should be recommenced initially with lower volume exchanges with or without omissi on of the ambulant day dwell if the patient is on APD and clearances allow. Persistent leak s require catheter change or surgical repair. Clinical features include slow drainage, which may be pre- dominantly slow drainage out, or alternatively slow in \202 ow (accompanied by slow out \202 ow if \202 uid infusion is possible). Investigations: \200 plain abdominal X-ray (which will show catheter posi- tion and presence of constipation); i njection of radiocontrast down catheter with screening (to show \202 ow of dialyzate and presence of adhesions); CT peritoneography. Hernias in PD Hernias are a relatively common complication of PD. Pre-existing hernias shou ld be repaired before commenc- ing PD. This may be combined with catheter insertion. They m ay also develop after starting PD as a complication of the increase in intra-abdominal pres sure. Sites include: \200 \200 \200 \200 \200 Management Laxatives improve slow drainage due to constipation and sometimes reverse cathet er migration. Heparin is instilled if catheter blockage results from \201 brin or blood, and urokinase may be used if heparin is ineffec- tive. Catheter repositioning may be attemp ted: \200 inguinal; para-umbilical/umbilical; catheter insertion site; other incision sites; ventral hernias. Problems include: \200 \200 radiologically (by passage of guidewire and attempts to move the catheter tip under X-ray s creening); open surgically; laparoscopically. \200 pain; risk of bowel incarceration and strangulation. If surgical intervention is required, partial omentectomy may be performed and the catheter can be sutured into the pelvis. Alternatively, the catheter may be removed and replaced. I f catheter change is required, temporary HD may be avoided by resting from dialysis for the usual catheter heal- ing time if residual renal function is suf \201 cient, or by earlier commencement of PD post surgery using small volume exchanges in supine position (e.g. APD with dry day). In cases of Gram-negative peritonitis one should always consider the possibility of bowel s trangulation as the her- nial ori \201 ce may not always be obvious. Management Management is by surgical repair. This may require a period of discontinuation o f PD and temporary HD. Some PD patients may have adequate residual function to allow a peri od without dialysis. It is also possible to recommence PD very soon after a hernia repair, especially when a mesh repair has been per- formed, with initial use of low dialyzate volum es in the supine position. Fluid leaks Pericatheter leaks Pericatheter leaks may occur early or late after tube inser- tion and may be precipitated by coughing, straining or heavy lifting. Presentation is with \202 uid leaking externally with wetness of the exit site or dressing. Hydrothorax Pleural effusions may occur for a number of reasons on PD. Pulmonary and pleura l disease may occur as in other sub- jects and it is also important to consider \202 uid overload and cardiac failure as causes in PD patients. Abdominal wall leaks Abdominal wall edema may also arise by leaking through the catheter si te or previous abdominal incisions. There may be induration or a spongy feeling of the abdo minal wall skin and peau d \200\231orange appearance. Patients may experience a loss of ult ra \201 ltration without change in transportation characteristics. Abdominal wall leaks ma y be demonstrated by CT perito- neography or MRI. Diaphragmatic leak Effusions may also occur due to peritoneo-pleural leakage of dialyzate w hen dialyzate passes through areas of de \201 - ciency in the diaphragm. This most commonl y occurs on the right side. The presence of an effusion may be identi \201 ed clinically a nd con \201 rmed on chest X-ray. Effusion size varies but may be large enough to cause res piratory dif \201 culties. Thoracocentesis should be performed with \202 uid undergo- in g standard biochemical, microbiological and cytological tests. The presence of low protein in keeping with a transu- date and high glucose content (greater than in blood) sug- gests the diagnosis. Management may include therapeutic pleural aspiration of pleural \202 uid and temporary discontinuation of PD. Occasionally a period of rest and recommencement of PD with initially smaller volumes may be successful. If the effusion recurs, pleurodesis may allow ongoing treat- ment with PD. Genital edema Genital edema is an uncommon but distressing complica- tion of PD. Mechanisms include tracking of \202 uid leaking around the catheter or an incision site via the sub cutaneous tissues or leak via a hernia or patent processus vaginalis. Investigations Diagnosis of any leak and identi \201 cation of the cause may include: \200 \200 \200 CT peritoneogram with intraperitonal contrast; MRI with dialyzate in situ; USS (may identif y the presence of herniae containing dialsate); abdominal scintigraphy (dialyzate containin g radiola- beled tracer). G. WOODROW 516 Other complications of PD Pain with PD exchanges In \202 ow pain In \202 ow pain is the m ost common problem. It may occur soon after commencing PD and disappear with time whilst co ntinuing PD. Persistent in \202 ow pain may relate to the low pH of standard PD \202 uid s and may improve with use of neutral pH solu- tions. An alternative is the use of tidal PD for patients on APD. Pain may relate to movement of the PD catheter out of its correct pos ition which can be diagnosed on AXR. Management includes: \200 \200 regular use of laxatives; patient education about the importance of avoiding con- stipation ; dietary \201 bre supplements. Encapsulating peritoneal sclerosis (EPS) This is a rare but serious complication of long-te rm PD. The incidence increases with time on PD. Patients develop marked \201 brotic thick ening of the perito- neal membrane forming a cocoon surrounding and binding the intestine. It may be preceded by a progressive increase in membrane transportation state. Although typ ically presenting in patients whilst on PD, it may still occur after the patient has been t ransplanted or transfered to HD. Out \202 ow pain Out \202 ow pain is less common. It may be due to peritonitis or be a te mporary phenome- non after commencing PD. Risk factors \200 \200 \200 \200 Back pain Back pain may occur or be exacerbated by the presence of PD \202 uid which alte rs normal posture. Other treatable or serious causes of back pain should be excluded by inv estigation. Reducing volumes of \202 uid in the abdomen during the day, which may involve transfer to APD with reduced daytime dwell volume, or NIPD with a dry daytime period may h elp.