***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Abstract Nitrofurantoin or methenamine hippurate was given prophylactically to elderly patients without urinary tract infection at the beginning of long-term catheterization ( mean 81 days ) , but it only delayed the appearance of bacteriuria . Escherichia coli was most frequently the first species to appear ( ≥10 4 /ml ) in the urine of 40 patients given methenamine hippurate as well as in the control group ( 41 patients ) , whereas in 42 patients treated with nitrofurantoin  more resistant species , such as Proteus mirabilis , Providencia spp . and Pseudomonas aeruginosa most often appeared first . Weekly tests made during the course of catheterization showed that E. coli disappeared from the nitrofurantoin-treated patients , while pseudomonas increased in this group and providencia in the control group . Pseudomonas was isolated more frequently in the nitrofurantoin than other groups . With the exception of klebsiellae , the bacterial strains isolated from the nitrofurantoin group were as sensitive to various antibiotics as were those from other groups . Significantly more sample s with growth of yeasts ( ≥10 4 /ml ) were obtained from nitrofurantoin treated than from methenamine hippurate treated patients . C and ida albicans was the species of yeasts most often isolated Are meta-analyses the brave new world , or are the critics of such combined analyses right to say that the biases inherent in clinical trials make them uncombinable ? Negative trials are often unreported , and hence can be missed by meta-analysts . And how much heterogeneity between trials is acceptable ? A recent major criticism is that large r and omised trials do not always agree with a prior meta- analysis . Neither individual trials nor meta-analyses , reporting as they do on population effects , tell how to treat the individual patient . Here we take a more rounded approach to meta-analyses , arguing that their strengths outweigh their weaknesses , although the latter must not be brushed aside In a r and omised , double blind , long term , crossover study 1 g twice daily of methenamine hippurate was compared with placebo for its preventive effect on recurrent attacks of acute cystitis .  Methenamine hippurate and placebo were interchanged every six months for two years . During one of the years patients took 250 ml extra fluid every morning and evening . Out of 21 enrolled patients , 14 completed the first year and 13 both years of treatment , which permitted the evaluation of 27 patient years . There were 52 episodes of acute cystitis caused by reinfection : 41 occurred during placebo treatment and only 11 during the methenamine hippurate regimen ( p less than 0.01 ) . Extra fluid intake did not reduce the incidence of acute cystitis , nor did it reduce the effect of methenamine hippurate . Methenamine hippurate is an effective prophylactic agent against recurrent acute cystitis and has the advantage of not inducing cross resistance to conventional antibiotics Objective : To determine whether Methenamine Hippurate ( MH ) or cranberry tablets prevent urinary tract infections ( UTI ) in people with neuropathic bladder following spinal cord injury ( SCI ) . Study design : Double-blind factorial- design r and omized controlled trial ( RCT ) with 2 year recruitment period from November 2000 and 6 month follow-up . Setting : In total , 543 eligible predominantly community dwelling patients were invited to participate in the study , of whom 305 ( 56 % ) agreed . Methods : Eligible participants were people with SCI with neurogenic bladder and stable bladder management . All regimens were indistinguishable in appearance and taste . The dose of MH used was 1 g twice-daily . The dose of cranberry used was 800 mg twice-daily . The main outcome measure was the time to occurrence of a symptomatic UTI . Results : Multivariate analysis revealed that patients r and omized to MH did not have a significantly longer UTI-free period compared to placebo ( HR 0.96 , 95 % CI : 0.68–1.35 , P=0.75 ) . Patients r and omized to cranberry likewise did not have significantly longer UTI-free period compared to placebo ( HR 0.93 , 95 % CI : 0.67–1.31 , P=0.70 ) . Conclusion : There is no benefit in the prevention of UTI from the addition of MH or cranberry tablets to the usual regimen of patients with neuropathic bladder following SCI Summary An evaluation has been made of the clinical and laboratory effects of short-term ( 34 days ) , high-dose ( 2 g × 3 daily ) treatment with methenamine hippurate ( MH ) of 14 geriatric patients with an indwelling catheter and clinical features of urinary tract infection . During MH treatment the number of catheter changes was halved , each catheter remaining in situ for an average of 12.0 days as compared to 6.2 days in the pre-treatment control period and 5.2 days in the post-treatment control period ; the difference is significant ( p=0.008 ; Friedman two-way analysis of variance ) . Urine pH was reduced ( pH 7.0–6.5–7.0 ; p=0.01 ) and the st and ard bicarbonate in blood was slightly elevated ( 24.1–25.7–25.0 mmol/l ; p=0.008 ) during the MH treatment period , when compared to pre- and post-treatment control periods . It is suggested that MH treatment reduced the complications associated with indwelling catheters due to reduction in urine pH , bacteriuria , and pyuria . Blockage of catheters is thought to be due to intraluminal salt precipitations with trapping of clumps , and is primarily not correlated with urine viscosity We conducted 202 trials in 161 male hospital patients to determine if prophylactic administration of ascorbic acid or antibacterials ( trimethoprim-sulfamethoxazole , nalidixic acid , methenamine hippurate or nitrofurantoin macrocrystals ) would prevent bacteriuria infections in spinal cord injury patients who had had at least 1 bout of bacteriuria . None of the drugs tested appeared to be statistically effective in the doses used in preventing bacteriuria in these patients . Moreover , sensitivities were lost to several drugs other than those used prophylactically . We conclude that use of prophylactic doses of ascorbic acid or antibacterials has not proved to be beneficial in spinal cord injury patients free of indwelling catheters Summary Catheterized patients with heavy bacteriuria and short catheter life received a shortcourse of antimicrobial therapy and then were allocated at r and om to double-blind treatment for 5 months with methenamine hippurate ( MH ) , 1 g three times daily , or placebo 1 g 3 times daily . MH treatment reduced the number of catheter blockages and instances of spontaneous removal of the catheter , and doubled catheter life ( p<0.001 ) . It is suggested that the doubled catheter life was due to the reduced bacteriuria and lowering of urinary Background . There is a high risk of  postoperative bacteriuria and urinary tract infection after gynecologic surgery .  Postoperative asymptomatic bacteriuria often disappears without treatment , but 15–20 % of patients still require treatment for postoperative urinary tract infection . This study was carried out to assess the value of prophylactic treatment with methenamine hippurate after routine gynecologic surgery Forty-two men with urinary tract infection and benign prostatic hyperplasia were r and omized into two groups before transurethral resection . One group ( 22 patients ) received Claforan ( cefotaxime ) peroperatively and thereafter daily for five days . In the other group ( 20 patients ) , Hiprex ( methenamine hippurate ) was given daily from the day before the operation , for a total of six days . All the bacterial isolates were sensitive to cefotaxime . The efficacy of the medication was clinical ly and bacteriologically evaluated . Postoperative temperature elevation ( greater than 38 degrees C ) occurred in one of the 22 patients in the cefotaxime group , and in nine of the 20 in the methenamine hippurate group ( p less than 0.05 ) . None of the former group , but two patients in the latter , had septicemia . The difference was not statistically significant . The response to treatment was satisfactory in 13 of the 22 patients in the cefotaxime group , but in only one of the 20 treated with methenamine hippurate ( p less than 0.005 ) . Antibiotic treatment is recommended for bacteriuric patients undergoing transurethral prostatic resection One hundred and twenty three elderly patients without urinary tract infection who required an indwelling urinary catheter because of cerebrovascular disease were divided into three groups . One was given methenamine hippurate ( MH ) , one nitrofurantoin ( NF ) , while a control group received no prophylactic urinary tract disinfectant .  Catheter complications , symptomatic urinary tract infections and the clinical course were recorded . At regular intervals bacteria were cultured from the urine , tests were made for antibody-coated bacteria ( ACB ) and routine laboratory investigations were performed . NF significantly delayed the appearance of ACB ; however , it did not prevent their appearance if a catheter was used for more than two months , by which time ACB were present in most patients irrespective of treatment . MH had less effect on the bacteriological findings , although it significantly decreased the need for antibiotic courses given for treatment of symptomatic urinary tract infections . In both MH- and NF-groups there were fewer patients with mechanical catheter complications . Forty seven patients died , generally due to cerebrovascular disease , and 22 autopsies were performed .  Gross inflammatory changes in the urinary tract were commonly found at autopsy in all groups if a catheter had been used for more than two weeks . A positive test for ACB considerably increased the probability of inflammatory changes in the kidneys , but because of the frequency of such changes after prolonged use of an indwelling catheter , the test does not seem to offer much advantage as a guideline for therapy . Prophylactic urinary tract disinfectants may not be warranted in all patients with an indwelling catheter . If , however , recurrent clinical complications such as clogging of the catheter or symptomatic infection occur , continuous use of a urinary tract disinfectant is indicated . MH is preferred because it has fewer side effects than NF A r and omised clinical study was carried out on patients admitted for ESWL treatment in order to establish the requirement for prophylactic treatment with antibiotics during this procedure . Patients with clinical signs of urinary tract infection , evidence of infectious stones or a positive urine culture were excluded . All other patients were consecutively r and omised into 3 groups which were given either trimethoprim + sulphamethoxazole or mecillinam ( Group A ) , methenamine hippurate ( Group B ) , or no treatment at all ( Group C ) . Evaluation with respect to clinical signs of infection was done immediately after the treatment and 4 weeks later . In addition , a urine culture was performed 2 weeks after ESWL , i.e. 1 week after completing treatment with antibiotics and methenamine hippurate . With respect to infectious complications there were no differences between Groups A and C , between Groups B and C or between Group A and B+C , whereas an unexplained slightly higher infectious rate was recorded for Group B compared with Group A. In all patients the occurrence of bacteriuria was low ( 6.7 % ) despite the fact that almost 30 % of patients had a ureteric catheter during the ESWL procedure . Patients with ureteric catheters did not present with more infectious complications than those without . All patients had a bladder catheter during ESWL . It was concluded that prophylactic treatment with antibiotics during ESWL treatment is unnecessary in all situations where an infectious aetiology is unlikely 290 patients with recurrent urinary tract infection were treated with either placebo , methenamine hippurate , nitrofurantoin or trimethoprim .  38.9 % of the patients had chronic pyelonephritis and 23.8 % azotemia . During the follow-up period of 1 year 63.2 % recurred in the placebo group , 34.2 % in the methenamine hippurate group , 25.0 % in the nitrofurantoin group and 10.4 % in the trimethoprim group . 62.5 % of the recurrences in the trimethoprim group were associated with trimethoprim-resistant strains . However , such strains appeared only in 6.5 % of the patients treated with trimethoprim , compared with 16.2 % in the placebo , 8.3 % in the nitrofurantoin and 11.0 % in the methenamine hippurate groups . Side-effects were mild and occurred most frequently in the nitrofurantoin group ( 13.9 % ) A prospect i ve study was performed to quantitate frequency and evaluate risk factors for urinary tract infection ( UTI ) in 64 catheter-free spinal cord injury ( SCI ) patients who were visited monthly in their homes for up to 1 year by a public health nurse who performed a physical examination and collected urine for culture and urinalysis . Patients also mailed in urine dip slides weekly . UTI was defined as > or = 100,000 
    Output:
    
Methenamine hippurate may be effective for preventing UTI in patients without renal tract abnormalities , particularly when used for short-term prophylaxis .
It does not appear to work in patients with neuropathic bladder or in patients who have renal tract abnormalities .
The rate of adverse events was low , but poorly described .