derlying urinary tract abnormality. Plain KUB allows monitoring of radio-opaque stones. \200 IVU offers an alternative if CT unavailable. \200 USS may be helpful if obstruction suspected and is also sensitive for stones in the renal pelvis but often misses ureteric stones. For considerations when stones occur in pregnancy, see b p. 860. CHAPTER 9 Essential urology 722 Stone disease: management Prevention of recurrent nephrolithiasis General measures: \200 Consider a specialist referral. Attendance at a stone clinic has been shown to reduce stone recurrence, independent of other factors! \200 Increase \202 uid intake for daily UO > 2.5L/day. Urine should appear clear, not dark and concentrated. Advise to: \200 Drink a large glass of water at speci \201 c times during the day, e.g. upon waking, arriving at work, etc. Drink a glass of fruit juice with breakfast. \200 Keep a large bottle of water at their w orkplace and sip from it regularly throughout the day. Drink a glass of water each hour, on the hour. \200 Add slices of lemon, lime, or orange to water. It improves \202 avour and helps to alkalinize the urine. Drink two full glasses of water at each meal (one before, one after). \200 Carry a re \201 llable water bottle everywhere \200\224 walking, shopping, driving, watching television, etc. Eat fruits and vegetables (contain a high amount of water). \200 Include more liquid and \200\230wet \200\231 foods in the diet, e.g. soups, stew, jellies, etc. Drink before bedtime. Aim to provoke nocturia at least once per night. Reduce animal protein intake: Protein ingestion l i acid formation l reduced urinary citrate excretion l less citrate available to form a soluble complex with calcium. It also generates sulfate ions that decrease calcium solubility. \200 Acidosis also decre ases tubular calcium absorption. \200 Protein metabolism increases uric acid production a nd encourages uric acid stone formation in low pH urine. Aim 0.8 \200\223 1.0g/kg/day animal protein (meat, poultry, \201 sh, eggs, cheese, yogurt), and advise regarding non-animal protein substitutes (lentils, chickpeas, k idney beans, butter beans, baked beans, quorn). Reduce Na + intake <3g/day (<6g/day NaCl). Na + enhances calciuria (partly explaining the increased incidence of hypercalciuria in hypertensive patients). Educate patients to understand salt content labeling on foods. Recommend a normal calcium intake of 7 700 \200\223 1,000mg/day. (cid:2) Many patients are erroneously told to reduce calcium ingestion. This risks osteopor osis (esp. \231\200 ) and may actually promote stone formation (low Ca 2+ intake l i oxala te absorption and excretion). Calcium supplement supplements should be avoided, however. Reduce dietary oxalate (see Table 9.4). \200 If uric acid stones, reduce dietary purine i ntake (see Table 9.4). \200 Increase intake of citrus fruits (a source of potassium citra te). \200 Avoid excessive vitamin C supplementation (increases urine oxalate). \200 Mon itor urinary stone screen for ef \201 cacy of therapy. STONE DISEASE: MANAGEMENT 723 Table 9.4 Dietary sources of oxalate and purine High oxalate Greens (e.g. spinach and kale), green beans, rhubarb, \201 gs, beetroot, cel ery, spring onions, leeks, okra, cocoa and chocolate, berries (including strawberries, blac kberries, etc.), plums, kiwi fruit, tangerines, lemons, tofu, soy milk, nuts, seeds, tea, c offee High purine (uric acid) Meat (particularly viscera, e.g. liver, kidney, heart), meat extrac ts (e.g. stock, broth, or gravy), anchovies, crab, oily \201 sh, such as sardines and mac kerel, shrimp, certain vegetables (including asparagus, cauli \202 ower, peas, spinach, mu shrooms), lentils, kidney beans, beer Speci \201 c measures Calcium oxalate/phosphate stones \200 If u-Ca 2+ normal: Potassium citrate 15 \200\223 30mmoL PO tds. \200 Potassium citrate increases urinary ci trate and urinary pH. Aim for a pH of 6.5. Higher might encourage calcium phosphate stones. Liquid preparations can be unpalatable, but tablet formulations (e.g. Urocit -K wax tablet ) are available (although more expensive). \200 The potassium salt is favored over the so dium salt, as the latter promotes calciuria. If u-Ca 2+ raised: Potassium citrate as for normal + either indapamide 2.5 \200\223 5mg PO daily or hydrochlo rothiazide 25 \200\223 50mg PO daily (monitor K + with both). \200 Thiazide diuretics in crease tubular Ca 2+ reabsorption (note: avoid triamterene, as it causes crystalluria itself). If d K + develops, add amiloride (for potassium). Recheck urinary citrate and calcium excretion after several weeks, and adjust appropriately. Hyperoxaluria \200 In malabsorption disorders, ensure adequate hydration. Hypocitraturia and hypokalaemia can occur and should be corrected. Colestyramine binds fatty acids and pre vents their delivery to the colon (where they would otherwise increase oxalate absorption). Pyridoxine (vitamin B6) can be helpful, although large doses may be required. Calcium carbonate 500 \200\223 1,500mg tds before meals may reduce oxalate absorption. Primary hyperoxaluria can only be cured by liver transplantation. Struvite stones Require vigorous eradication of infection; antibiotic therapy is often pro- longed, e.g. 3 \200\223 6 months, directed by cultures and sensitivities. Cystine stones (see b p. 719). Hyperuricosuria Complete dissolution of uric acid stones can often be achie ved, using a combination of high \202 uid intake, urinary alkalinization (pH >6.5), reduc ed dietary purine intake, and, if necessary, allopurinol 100 \200\223 300mg PO daily. CHAPTER 9 Essential urology 724 Acute renal colic Presentation The syndrome caused by stone(s) passage down the urinary tra ct. Typically \231\202 aged 20 \200\223 40. Colicky abdominal pain ( 2 often very severe) , radiating from loin to groin (especially as the stone moves toward the vesicoure- teric j unction). Often abrupt onset, with progressive increase in inten- sity. Nausea and vomiting common. Renal angle tenderness, haematuria (often macroscopic), dysuria, strangury, freque ncy 9 symptoms of UTI. 2 Patients may be systemically unwell at presentation, with dehydrat ion and d BP. Predisposing factors include dehydration and exercise. Renal colic may also b e caused by ureteric clots and papillary necrosis ( b p. 585). Investigations \200 Dipstick urine for haematuria (microscopic haematuria is almost universal) as well as leucocytes and nitrites. \200 Urine microscopy for crystals. MSU fo r M,C+S. \200 SCr, U&E, CRP, FBC ( 2 blood cultures if signs of infection). \200 CT-KUB to con \201 rm diagnosis, locate the stone, exclude obstruction, and predict response to lithotripsy. IVU if CT unavailable. Plain AXR may reveal radio-opaq ue stones ( 7 80%). (cid:2) A stone may be an incidental \201 nding. Have you considered other causes of pain? Management \200 3 Infection 9 obstruction are indications for urgent intervention. \200 Analgesia: NSAIDs (e.g. diclofenac 75mg IM or via suppository) are often very effective (use with caution, i.e. correct dehydration; monitor renal function wi th prolonged use). Opiates may also be necessary, e.g. diamorphine 2.5 \200\223 10mg SC/IM ) (with antiemetic, e.g. metoclopramide 10mg IM/IVI or cyclizine 50mg IM). Desmopressin can reduce pain in many patients (antidiuretic effect ameliorates proximal ure teric distension). It acts quickly and has minimal adverse effects. Usually 1 x 40 microgra ms dose administered nasally. Oral rehydration. If vomiting, IVI 0.9% NaCl for UO >2L/day. No role for \200\230forced hydration \200\231 to assist stone passage. If stone \211 5mm, 7 70 \200\223 80% will pass spontaneously. 50% if 5 \200\223 10mm. Majority of larger stones will not. Location is important: more distal stones pass 7 75% of the time, proximal 7 25%. Most pass in 1 \200\223 3 weeks. A adrenoceptor blockade, e.g. tamsulosin 400 micrograms od for 4 weeks, has been shown to i ncrease rate of passage (by 7 30%), particularly for distal ureteric stones. Termed \200 \230medical expulsive therapy \200\231 (MET). Proximal ureteric stones <20mm are best treated with ESWL ( b p. 725). ESWL access to stone s in the middle and distal ureter may be restricted by the pelvic bones, and ureteroscopy p rovides a very effective alternative. Percutaneous (and rarely open) nephrolithotomy have e xcellent results for calculi >20mm or complicated stones. ACUTE RENAL COLIC 725 2 If associated infection, co-amoxiclav IVI, then PO, or third-generation cephalosporin IVI, then PO, or \202 uoroquinolone (e.g. cipro \202 oxacin 250 \200\223 500mg bd PO). Consider additional single-dose gentamicin 3 \200\223 5mg/ kg IVI. Discuss w ith microbiology. 3 An obstructed, infected system caused by stones (pyonephrosis) is an emergency. Septicaemia 9 shock can supervene rapidly. \200 Commence IVI antibiotics and \202 uid resuscitation immediately. Discuss with urology, and arrange an urgent referral for percutaneous nephrostomy and drain age ( b p. 734). Surgical management of stone disease: a primer Surgical management of renal stone disease h as changed signi \201 cantly with the growth of minimally invasive techniques. In general, open surgi- cal techniques have been relegated to second, even third, line. \200 Extraco rporeal shock wave lithotripsy (ESWL): Acoustic shock wave energy is delivered under \202 uoroscopic or USS guidance. 1,500 \200\223 2,500 shock waves are delivered during each session (typicall y 7 30min). It is an ambulatory procedure but requires analgesia and (often) IV sedation. It can be repeated at 10 \200\223 14 day intervals. Fragmentation is followed by clearance of fragments. Multiple large fragments can block the ureter \200\224 termed Steinestrasse or \200\230Stone Street \200\231 . For stones >20m m, a ureteric stent is placed \201 rst. \200 Achieves very good rates of stone clearanc e for stones \211 20mm. \200 ESWL is now \201 rst-line in most cases, except larger (> 10mm), more distal ureteric stones where ureteroscopy is preferred. Success depends on the operator, equipment, stone characteristics (size, location, type \200\224 cystine and calcium oxalate stones are more dif \201 cult to shatter), and patient obesity. \200 Contraindications: AAA, pregnancy, bleeding tendency, UTI. \200 Side effects: hemorrhage, haematoma, adjacent organ damage. Ureteroscopy: Increasingly small, \202 exible ureteroscopes are allowing access to the entire urinary t ract. Stones are shattered, using a holmium laser, and the fragments can be retrieved. More rigid scopes and basket techniques are no longer favored. Percutaneous nephrolithotomy (PCNL): Suitable for larger or proximal ureteric stones. \200 A sheath is passed into the pelvica lyceal system percutaneously (usually the dorsal calyx of the lower pole, although higher p unctures allow antegrade ureteroscopy). Laser or USS is used to fragment the stone or it is removed under direct vision. Also allows chemolysis \200\224 the infusion of an alkaline solution to dissolve stones (usually uric acid). Less commonly used. Open surgery is now rarely necessary. Laparoscopic techniques are increasingly popular. CHAPTER 9 Essential urology 726 Obstruction: overview \200 2 Urinary tract obstruction is a common, and potentially rever sible, cause of both acute kidney injury and chronic kidney disease. Obstruction leads to delayed urinary transit, an increase in intratract pressures, and renal dysfunction. It will eventually cause dilatation of the renal pelvis and calyces. This is referred to as hydronephrosis. Obstruction causes renal failure when bilateral or when it involves a single functioning kidney. Obstruction accounts for 7 5% of ESRD in those aged >65. De \201 nitions \200 Obstructive uropathy: the structural or functional changes in the u rinary tract that impede the normal \202 ow of urine. Classi \201 ed according to site, degree, and duration. May be complete or partial. \200 Obstructive nephropathy: the kidne y disease resulting from impaired urinary \202 ow and consequent renal parenchymal damage. Hydronephrosis: upper tract dilatation. Obstruction is not the only cause but is the common est and must always be excluded. 2 May not always be present in obstruction, particularly i n early stage. Epidemiology Etiology and frequency varies with age and sex (see Table 9.5). Table 9.5 Epidemiology of obstruction Age Sex \231\202 > \231\200 \231\200 \231\202 > \231\200 \231\202 Etiology <10 >20 Congenital abnormalities; urethral valves, PUJ obstruction Pregnancy and gynecological mali gnancy Renal calculi Prostatic disease >60 Classi \201 cation \200 Cause (see Table 9.6): Congenital, e.g. urethral valves. \200 Acquired, e.g. prostatic disease. Level: Upper tract: ureter or above. \200 Lower tract: bladder or below. Unilateral or bilateral: Both kidneys are usually involved in lower tract obstruction. \200 An individual kidney c an be affected by upper tract obstruction. Complete or partial: Complete: 2 commonest cause of anuria. \200 Partial: can be dif \201 cult to diagnose, a s urine output may vary. Intrinsic or extrinsic: Intrinsic: arising within the urinary tract, e.g. stone disease. \200 Extrinsic: arising externally, e.g. retroperitoneal \201 brosis. OBSTRUCTION: OVERVIEW 727 Table 9.6 Causes of urinary tract obstruction Level of obstruction Obstruction within the lumen Obstruction within the wall Extrinsic compression Lower polar renal vessels crossing at PUJ Tumors Cysts Anatomical abnormalities, e.g. PUJ obstruction Kidney Calculi Sloughed papillae (diabetes mellitus, sickle cell trait/ disease, analgesic nephrop athy, acute pyelonephritis) Prostatic malignancy Ureter Calculi Uroepithelial malignancy Retroperitoneal malignancy (metastases, lymphoma) Stricture (malignant, post-surgery/ radiotherapy, TB, schistosomiasis) Retroperitoneal \201 brosis ( p or s ) Vascular, e.g. aneurysmal aorta or iliacs, congeni tal retrocaval right ureter VUJ obstruction Inadvertent surgical ligation Pregnancy Pelvic malignancy (e.g. cervical cancer) Bladder neck Calculi Uroepithelial malignancy Blood clot retention Uterine and ovarian masses Functional obstruction from neurological damage (e.g. DM, MS, spinal trauma) or drugs (e.g. anticholinergic) Blocked catheter Pelvic in \202 ammation Prostatic enlargement Urethra Calculi Stricture (congenital meatal stricture, or acquired \200\224 usually post-infective, or po st-surgical) Blood clots Urethral valves Tumors Calculi can be found anywhere along the urinary tract but most commonly at the ureteropelvi c or vesicoureteric junctions. ** Blood clots may be caused by bleeding renal tumors, surge ry, AV malformations, renal trauma (including renal biopsy), adult polycystic kidney diseas e, and traumatic catheterization. CHAPTER 9 Essential urology 728 Obstruction: pathophysiology Normal physiology Urine production is continuous, and it reach es the bladder as a result of several processes: \200 Glomerular \201 ltration pressure . \200 Renal tract peristalsis. Pacemaker cells in the renal calyces initiate contraction of the renal pelvis. Subsequent coordinated ureteric smooth muscle contraction directs uri ne toward the bladder. Pressures reach 20 \200\223 80cmH 2 O (resting pressure is 0 \200 \223 5cmH 2 O). Gravity. \200 The vesicoureteric junction (VUJ) prevents retrograde ureteric urine \202 ow during bladder contraction. Pathophysiology \200 There is a relationship between ureteric pressure and renal blood \202 ow. Following an initial increase in both (minutes), further increases in ureteric p ressure result in a reduction in renal blood \202 ow (hours). \200 This mismatch progre ssively widens, with consequent ischaemic injury. \200 Impaired glomerular and tubular fu nction result. Glomerular \200 Proximal tubular pressure rises early. \200 This causes a net d in hydr aulic pressure gradient across glomerular capillaries and a signi \201 cant reduction in GFR. Afferent arteriolar vasoconstriction (mediated by i angiotensin II and i thromboxane A 2 + d NO and d vasodilator prostaglandins) reduces both renal plasma \202 ow and glomerular c apillary pressure. Blood is redirecting away from non- \201 ltering nephrons. \200 Ischaemic nephrons relea se mediators of in \202 ammation, leading to macrophage in \201 ltration, interstitial \201 brosis, and irreversible injury. Tubular \200 Tubular dysfunction often manifests after the resolution of obstruction. \200 Includes reduced urinary concentrating ability ( d expression of both Na + transporters + aquaporins), abnormal electrolyte handling (mild Na + wasting and i K + excretion), and acidosis ( s to abnormal intercalated cell H + ATPase activity). In lower tract obstruction, the normally protective VUJ is rendered incompetent, allowing retrograde transmission of pressure. Hypertrophy of the ureteric musculature attempts to compensate for the increased resistance. The ureter becomes stretched and tortuous, resulting in ureteric distension and hydronephrosis. Fibrous bands develop along the length of the ureter, adding a further element of obstruction that may persist after the resolution of the original cau se. Histopathology \200 Initial changes are of renal enlargement with oedema and pelvicalycea l dilatation. OBSTRUCTION: PATHOPHYSIOLOGY 729 This advances to encompass distal tubular dilatation, proximal tubular cell atrophy, and, e ventually, enlargement of Bowman \200\231 s space, with periglomerular \201 brosis. Continuing damage is essentially a form of ischaemic injury, with macrophage-derived TGF- B fueling progressive, irreversible tubulointerstitial \201 brosis. Unresolved obstruction eventually causes macroscopic change, characterized by dilatation of the renal pelvis, \202 attening of the papillae, and gradu al thinning of the cortex and medulla. Recovery of renal function \200 The prognosis post-relief of obstruction is contingent on antecedent duration and severity. Available clinical and experimental evidence suggests that full recovery of renal function is possible after complete obstruction \211 7 days \200\231 d uration. There may be some functional recovery after 4 weeks, but signi \201 cant permanent renal damage is usually present beyond 6 weeks. Dialysis support is likely to be needed during this time. 3 This underlines the need for prompt diagnosis and treatment of acute obstruction if perma nent renal damage is to be avoided. \200 The SCr and eGFR may underestimate the extent of parenchymal damage, with the hyper \201 ltration and hypertrophy of remaining nephrons ma sking nephron scarring and dropout. This is particularly relevant to unilateral obstruction where the contralateral kidney compensates to maintain function. In more chronic, or partial, forms of obstruction, renal parenchymal changes are likely to be well established, so return of renal function is unpredictable, at best. The renal corti cal thickness on ultrasound (or other imaging) may give some indication of the potential to salvage GFR, but a degree of CKD is often inevitable. However, subsequent progression of CKD is often relatively slow, providing BP is well controlled. Evidence of tubular dysfunction often persists after the relief of chronic obstruction and can be clinically relevant, e.g. polyuria, mild salt wasting, and a cidosis. CHAPTER 9 Essential urology 730 How to approach obstruction 3 It is vital that obstruction is considered and actively exclu ded in all presentations of AKI and many of CKD. An accurate history may provide clues as to whether the obstruction is acute/chronic, unilateral/bilateral, congenital/acquired. Clinical presentation Symptoms Depend on the cause and level of obstruction. (cid:2) Unilat eral obstruction and chronic partial obstruction can be clinically completely silent. \200 Loin pain: Flank pain suggests upper tract obstruction. Acute ureteric colic can be severe. It is usua lly unilateral and may radiate to the ipsilateral groin ( b p. 724). 2 Flank pain, fever, and signs of pyelonephritis suggest obstruction with infection ( l requires emergency decompression of the affected system). Pain radiating to the \202 ank during micturition is suggestive of vesicoureteric re \202 ux ( b p. 712). Pain after high-volume \202 uid intake (e.g. beer!) occurs in pelvi-ureteric junction (PU J) obstruction ( b p. 736). \200 Retroperitoneal \201 brosis may cause backache ( b p. 738). Haematuria: Macroscopic haematuria occurs with calculi and uroepithelial tumors. Changes in urine volume: 2 Complete anuria should always suggest obstruction. \200 Polyuria can be a feature of pa rtial obstruction. Lower urinary tract symptoms (LUTS) suggest bladder dysfunction or out \202 ow obstruction. \200 Obstructive (voiding) symptoms: reduced urinary stream, he sitancy, interrupted \202 ow, incomplete emptying, acute retention. Storage ( \201 lling) symptoms: nocturia, daytime frequency, urgency, incontinence, dysuria. Any patient presenting with CKD 3 or above with signi \201 cant LUTS warrants a urinary tr act ultrasound (including pre-/post-voiding). UTI: Obstruction l urinary stasis l infection. \200 Obstructed urine is dif \201 cult to ster ilize with antimicrobials. \200 A single UTI in a child or an adult \231\202 is suspicio us and should be further investigated. Recurrent infections in a \231\200 should prompt th e same. Signs \200 Palpable bladder ( (cid:2) you will miss it if you do not look for it!). \200 Loin tenderness. \200 Flank mass (palpable hydronephrosis in a thin or young patient). HOW TO APPROACH OBSTRUCTION 731 Blood pressure: i BP ( l mediated via renin or salt and water retention in CKD). \200 d BP ( l polyuria w ith salt and water wasting). Rectal and pelvic examinations may (often) be necessary. Investigations \200 Urinalysis: Haematuria, leucocytes, nitrites. \200 Proteinuria, when present, is usually low-grade. \200 Bland urine, free of blood or protein, can point toward obstruction during the invest igation of renal impairment, as it makes an intrinsic renal lesion less likely. MSU for M,C+S. \200 Electrolytes: Mild acidosis, with associated hyperkalaemia. Creatinine, eGFR: Remember \200\224 these can be falsely reassuring in unilateral obstruction. CRP, WCC, blood cultures for infection. \200 Consider a PSA in \231\202 with marked LUTS ( b p. 772). \200 Imaging ( b p. 732). CHAPTER 9 Essential urology 732 Obstruction: imaging Imaging is fundamental to the accurate diagnosis of the site and cause of obstruction. Ultrasound is usually \201 rst-line, but other modalities may be necessa ry to further progress management. 2 No single investigation can be considered to have completely excluded obstruction when cl inical suspicion remains high. Ultrasound (USS) See Fig. 9.1. \200 Portable, rapid, and non-invasive. \200 Can measure pelvicalyceal diameter. \200 May demonstrate dilated upper ureters. \200 No contrast o r radiation, so the imaging of choice in patients who have renal impairment or are pregnant. However, USS is operator-dependent, and obstruction (particularly early) can occur without a dilated system (<35% of patients with proven obstruction). Moreo ver, a dilated system demonstrates hydronephrosis, which is not the same as proving obstruc tion (see Box 9.2). Box 9.2 Ultrasound and obstruction: the pitfalls Obstruction without a dilated system (false negative) \200 Hydronephrosis may not be appa rent in early ( \201 rst 2 \200\223 3 days) obstruction. Dilatation may not occur if retroperitoneal tumor or \201 brous tissue encases the kidney. \200 ATN may coexist. \200 ATN l oligo-anuria l no hydronephrosis d evelops. \200 Partial obstruction may not cause a demonstrable hydronephrosis (although GFR is still reduced). Dilated system without obstruction (false positive) \200 Anatomical variants: extrarenal pelvis, megaureter (often secondary to vesicoureteral re \202 ux) ( b p. 712). Pregnancy: progesterone effects on smooth muscle can cause dilated ureters and pelvis. Post obstruction: an abnormal \200\230baggy \200\231 system may persist after the resolution of chronic obstruction. Comparison with previous imaging will be helpful in this situation. Further imaging (CT or isotope renography) may be necessary. CT \200 Highly sensitive for calculi. A non-contrast CT-KUB is now the investigation of choice for acute \202 ank pain ( b p. 724). Superior anatomical de \201 nition to USS. More likely to demonstrate site and nature of o bstruction. If clinical \201 ndings and USS equivocal, CT KUB is most likely to provide t he most information on the site and cause of the obstruction. OBSTRUCTION: IMAGING 733 Particularly helpful for the diagnosis of extrinsic compression and retroperitoneal \201 brosis, as well as the staging of tumors. IV contrast improves diagnostic utility, (cid:2) but take care to reduce the risk of contrast nephropathy in the presence of renal impairment ( b p. 148). Fig. 9.1 Renal ultrasound appearances of acute obstruction with pelvicalyceal dilatation. R eproduced with permission from Warrell D, Cox T, Firth J, and Benz EJ (eds) (2004) Oxford T extbook of Medicine , 4th edn, p.451. Oxford University Press, Oxford. Intravenous urography (IVU) Increasingly redundant. Previously used to determine the level of obstruc- tion through delayed \201 lms (e.g. 20min, 1h, 2h, 4h, 8h). However, this is rarely necessary, and, if desirable, a CT-IVU would generally be preferred. MRI \200 MR urography provides detailed anatomical information. \200 Also offers helpfu l functional information, including renal transit times. \200 (cid:2) No ionizing radiati on, but the potential for gadolinium to cause nephrogenic systemic \201 brosis (NSF) restricts its routine use in higher stages of CKD ( b p.51). Useful if known contrast allergy. Isotope renography (with diuretic) \200 A DTPA or MAG-3 renogram ( b p.54) may show delay ed isotope excretion in the presence of obstruction. The addition of a loop diuretic can differentiate between simple dilatation and true obstruction. Normally, the diuretic, administered 30min after the isoto pe, would cause prompt washout from the kidney. Persistence suggests obstruction. Excretion of both kidneys can be compared. Also estimates split function and may contribute to the assessment of whether attempts to s alvage a kidney are likely to be worthwhile. \200 (cid:2) Sensitivity decreases if renal function is signi \201 cantly impaired. CHAPTER 9 Essential urology 734 Obstruction: treatment Overview 2 Effective interdisciplinary communication between nephrol ogy, urology, and radiology is essential. Management is directed by: (i) the site, duration, and cause of obstruction; (ii) the prese nce of infection; and (iii) the degree of metabolic disturbance. Treatment goals \200 Treat any emergent metabolic or \202 uid and electrolyte disturban ces, e.g. i K + , pulmonary oedema. This may require dialysis or CRRT; 2 Seek expert help. 2 If there is evidence of sepsis (fever, abnormal urinalysis or urine microscopy, i WCC, i CRP, shock), then take appropriate cultures, and treat urgently. Prompt relief of obstruction to prevent further metabolic disturbance and protect the kidney(s) from irreversible renal damage. \200 If the duration of obstruc tion is unclear, assume it is acute. \200 If a single kidney is obstructed, do not be rea ssured by preserved GFR \200\224 the obstructed kidney may still need urgent intervention. Manage the underlying pathology, e.g. recurrent stones, tumor. Relief of obstruction \200\224general principles \200 Bladder out \202 ow obstruction ca n often be relieved with a urinary catheter. If this cannot be passed per urethra, a suprapubic catheter may be necessary. In an emergency situation or if infection above the obstruction is suspected, upper tract obstruction should be relieved through the placement of a percutaneo us nephrostomy under LA. Subsequent antegrade stenting of the obstruction through the nephrostomy may be possible. In non-emergency situations and when the patient is \201 t for GA, cystoscopic placement of retrograde ureteric stents is an appropriate approach. Urinary catheters and ureteric stents require follow-up and elective replacement. (cid:2) Be vigilant for infection or blockage. Percutaneous nephrostomy Is it necessary? \200 Pros: Decompresses an obstructed system and rapidly improves renal function. Decompression of one kidney should be suf \201 cient initially (preferentially decompress the kidney with the most parenchyma visible on imaging \201 rs t). Will decompress an infected system with minimal instrumentation. \200 No GA required. \200 Allows time for a more de \201 nitive management plan to be developed. OBSTRUCTION: TREATMENT 735 Cons: Invasive. Potential complications: bleeding and infection. \200 Not always available 24 h ours a day (although it should be). \200 Temporary although can occasionally be left long -term in those un \201 t for further intervention or on a palliative treatment pathway. How urgent is it? \200 Obstructed infected urinary system l 2 emergency nephrostomy required. If severe renal failure, K + >6.0mmol/L, or pulmonary oedema, then dialysis prior to a nephrostomy may be desirable. 2 Seek expert help. \200 Once a patient is safe, a delay of hours to ensure an expert operator may be justi \201 ed. How should I prepare the patient? U&E, FBC, clotting screen, G&S. Liaise closely with the i nterventional radi- ology team. They should gain informed consent. Post-procedure care \200 Regular post-nephrostomy observations and clinical review are mandatory, particularly in the presence of sepsis. Careful \202 uid balance: there is likely to be a brisk post-obstructive diuresis. See Post-obstructive diuresis below. \200 Make sure the nephrostomy is well sec ured! \200 As well as being therapeutic, a nephrostomy also has diagnostic potential. A n ephrostogram involves injection of contrast via the nephrostomy to examine antegrade ureter ic \202 ow and identify the level and source of obstruction. Post-obstructive diuresis \200 A large-volume diuresis (0.5 \200\223 1L/h) post-relief o f obstruction. \200 Most common after the treatment of bilateral obstruction or obstruction of a single functioning kidney. Results from either: Appropriate excretion of retained salt and water in renal failure, or Inappropriate losses due to tubular dysfunction. Consequences: salt loss, volume depletion, electrolyte disturbances, ATN with delayed recovery of renal function. Management: Regular assessment of \202 uid balance, including BP, hourly UO, clinical assessment, daily weights. Regular U&E (12-hourly if diuresis large). Also monitor K + , bicarbonate, calcium, phospha te, and magnesium daily. Fluid replacement: Once euvolaemic , administer IVI 0.9% NaCl as UO + 50mL/h. Replace electrolytes, as necessary. \200 (cid:2) Remember the diuresis may initially resu lt from the appropriate excretion of the salt and water retained during obstruction. The ai m is not to perpetuate \202 uid overload, but to prevent volume depletion. CHAPTER 9 Essential urology 736 Pelvi-ureteric (PUJ) obstruction De \201 nition \200 Proximal obstruction at the ureteri c junction of the renal pelvis, resulting in reduced or absent urinary \202 ow and a high-pressure renal pelvis. \200 May coexist with vesicoureteric re \202 ux ( b p. 712) or VUJ obstruction. Etiology May present antenatally, in childhood, or in adults. \200 Congenital: Intrinsic: \231\202 > \231\200 , proximal ureteric developmental defect. \200 Extrinsic (rare): external compression (e.g. aberrant renal vessel). Acquired: Intrinsic: stricture (infection, trauma), uroepithelial malignancy. \200 Extrinsic: malig nancy, retroperitoneal \201 brosis. Symptoms and signs \200 Increasingly diagnosed with maternal USS screening. It is the mos t common cause of antenatal hydronephrosis ( 7 1 in 1,500 live births). L > R but may be bila teral. Children may present with failure to thrive, \202 ank pain, urinary tract infections, a palpable mass, haematuria, hypertension, or renal impairment (if bilateral). 20% diagnosed as adults (with a large number presumably never diagnosed at all). Classically causes \202 ank pain after alcohol, coffee, or diuretics ( Diettel \200\231 s crisis). Investigation \200 USS (preferred) or CT will show dilatation of the renal pelvis with a normal distal ureter. Diuretic isotope renography demonstrates obstruction with delayed \200\230washout \200\231 . Serial scans are performed to determine optimal management. \200 Micturating cystouretero gram (MCUG) may demonstrate concomitant VUJ obstruction or posterior urethral valves. Management \200 No randomized trials: Generally conservative unless: impaired renal function (often manifesting as a change in split renal function), recurrent UTIs, calculi, persistent pain, increasing hydronephrosis. Prophylactic antibiotics of little bene \201 t. Surgery: Pyeloplasty involves resecting the abnormal ureteric segment and reattaching normal ureter to the renal pelvis. Various techniques are available, including open, laparoscopic, and en doscopic. All are very successful. If the obstruction is due to aberrant vasculature, the PUJ is repositioned above the vessel . PELVI-URETERIC (PUJ) OBSTRUCTION 737 Vesicoureteric junction obstruction \200 VUJ (like PUJ) obstruction can be congenital or acquired. \200 It may present with a similar constellation of symptoms to PUJ obstruction but often later in childhood or as an adult. It is very important to look for associated VUR ( b p. 712) and PUJ obstruction. If surgery is necessary, it involves re-implantation of the ureter. Posterior urethral valves (PUV) \200 A developmental abnormality in males, leaving obstru cting membranous folds in the lumen of the posterior urethra. The most common cause of urinary obstruction in infants ( 7 1 in 8,000). \200 The most co mmon cause of CKD due to obstruction in children ( 7 15% progress to ESRD). PUV cause dilatation of the proximal urethra, with hypertrophy of the bladder wall, bilateral megaureters, and hydronephrosis. \200 Most are identi \201 e d by antenatal USS (bilateral hydronephrosis, dilated bladder, and dilated posterior urethr a: \200\230keyhole sign \200\231 ). Associated with other abnormalities, including urinary tract (VUR, renal dysplasia) and non-urinary tract (e.g. lung hypoplasia). \200 Children present with failure to thrive, abdominal distension, UTIs, incontinence (daytime and nocturnal enuresis), and other urinary symptoms, including frequency, straining, poor stream, and large voids. MCUG is used to con \201 rm diagnosis. \200 Management includes urinary drainage in the newborn, usually by catheterization. Cystoscopic resection of the PUV should be undertaken as early as possible. Fetal intervention is now being undertaken in some specialist centers for severe cases. If PUV ablation is not possible, then a vesicostomy or other form of urinary drainage procedure should be considered. Bladder dysfunction is common and often persistent, requiring ongoing management, such as clean intermittent catheterization. CHAPTER 9 Essential urology 738 Retroperitoneal \201 brosis: overview Overview \200 Retroperitoneal \201 brosis (RPF) describes a group of disorders characterized by the development of \201 broin \202 ammatory tissue that surrounds and e ncases the abdominal aorta and other retroperitoneal structures, including the ureters. Encasement impairs ureteric contractility and causes an obstructive uropathy and then nephropathy. There are idiopathic (70%) and secondary forms. Both are uncommon ( 7 1 per 200,000 \200\223 500,000 population). The idiopathic form usually occurs age 40 \200\223 60, with a 3:1 \231\202 : \231\200 ra tio. Etiology \200 p and s RPF are usually very similar pathologically. \200 A tough, plaque -like material encases the major vessels and ureters. \200 Microscopically, there is a ma crophage- and plasma cell-rich in \202 ammatory in \201 ltrate, with progressive \201 b rotic change. \200 This \201 brous tissue consists of \201 broblasts (including activ ated myo \201 broblasts) and type I collagen. The causes of this process remain poorly understood. Suggestions: \200 They are an in \202 ammatory reaction to aortic atherosclerosis. Evidence: leakage of proin \202 ammatory lipid-derived material, such as ceroid (an oxidiz ed LDL) across the wall of atheromatous aortas. \200 It is an autoimmune phenomenon. Evid ence: coexisting autoimmune conditions, autoantibodies (60% ANA +ve in one series), HLA associations (HLA-B27 or HLA-DR B1 03). Causes \200 Idiopathic. \200 In \202 ammatory periaortitis (severe atherosclerosis), e .g. aortic aneurysm. \200 Drug-induced: classically methysergide, but also bromocriptine, methyldopa, and possibly beta-blockers. Chronic retroperitoneal infection (particularly TB). \200 Other in \202 ammatory conditi ons (e.g. sarcoidosis). \200 After retroperitoneal trauma. \200 Erdheim \200\223 Chest er disease: a rare histiocyte disorder, characterized by osteosclerotic bone lesions. Extra skeletal effects may include retroperitoneal in \201 ltration. Malignant: Lymphoma, lymphoproliferative disorders, carcinoid. \200 Metastatic or locally invasive m alignancies (e.g. colon). \200 Post-radiotherapy. Clinical features \200 Symptoms may be insidious and present >6 months prior to diagnosis (which is often considered only when i SCr becomes apparent). \200 Usually non-speci \201 c, e.g. malaise, anorexia, fever, and weight loss. \200 Flank and low back pain are relatively common. RETROPERITONEAL FIBROSIS: OVERVIEW 739 Vascular encasement may produce oedema or claudication. \200 Associations: in \202 ammat ory bowel disease, sclerosing cholangitis, ankylosing spondylitis, SLE, scleroderma, vascul itides, Raynaud \200\231 s. An association is also emerging with the relatively new clinicopathological entity of IgG4-related sclerosing disease. This has been described in v arious tissues, particularly pancreatic ( \200\230 autoimmune pancreatitis \200\231 ), an d is characterized by i circulating IgG4 as well as IgG4 plasma cell-rich in \202 ammatory in \201 ltrates. Investigations \200 FBC (normocytic normochromic anemia). \200 U&E, SCr, eGFR (impaired renal function). \200 ESR (a consistent marker of in \202 ammation, useful for monitori ng). \200 CRP. \200 ANA and other autoantibodies (variably +ve). \200 Immunoglobulins (polyclonal hypergammaglobulinaemia). \200 High serum IgG4 concentration. \200 Urinaly sis is typically bland. Imaging \200 USS will demonstrate uni- or bilateral hydronephrosis. \200 CT shows \201 brotic plaque enveloping the aorta and IVC and extending laterally to encompass the ur eters (see Fig. 9.2, b p. 741). May also show associated atherosclerosis and aneurysmal cha nge. Metastatic deposits, hemorrhage, and other disorders can have