Impaired Bone Growth After Ileal Augmentation Cystoplasty

Bladder augmentation and urinary diversion in patients with neurogenic bladder: non-surgical considerations

Segments from almost all parts of the bowel have been used for urinary diversion. As a result, the available absorptive surface area of the bowel is reduced, and the incorporation of bowel segments into the urinary tract may have metabolic consequences. This is an area somewhat neglected in the literature. Metabolic complications are rare, but sub-clinical metabolic disturbances are quite common. Several studies have demonstrated that some of the absorbent and secreting properties of the bowel tissue are preserved after incorporation into the urinary tract. Hyperchloraemic metabolic acidosis can occur if ileal and/or colon segments are used, as well as malabsorption of vitamin B(12) and bile acid after the use of ileal segments. These metabolic effects are not as severe as may be suspected and can be prevented by prophylactic substitution. Secondary malignancies can develop as a long-term consequence of bladder augmentation. Using colonic segments, tumours are most likely to occur at the ureteral implantation site. To prevent metabolic complications, careful patient selection and meticulous and lifelong follow up, as well as prophylactic treatment, are mandatory. Endoscopy for early detection has been recommended, starting 10 years postoperatively for patients who underwent surgery for a benign condition.

Animal models in urinary diversion

We set out to critically assess the value of animal experimentation in urinary diversion through intestinal segments, as some authors question the effectiveness of animal research, criticising the methodological quality, lack of standardization, inadequate reporting and the few systematic reviews in this field. Based on a comprehensive MEDLINE literature search (MeSH database; search terms: urinary diversion, urinary reservoirs, continent, rat, dog, animal models) we retrieved and evaluated all full-length papers published in English, German, French, and Spanish languages from 1966 to 2011 reporting the use of animal models in the setting of urinary diversion. Studies were stratified according to the addressed research question. Within each category species, gender, number of animals, age at procedure, type of diversion, mortality, length of follow-up, experimental procedure and outcome were recorded and tabulated. In all, 159 articles were judged to be relevant and while there are numerous animal models only a few have been used in more than one study. Animals were used for the systematic study of new surgical techniques (93 articles) or metabolic and functional consequences of urinary reconstruction (66 articles). For the latter purpose, the most often used animal is the rat, whereas the dog model is preferred for technical experimentation. In many studies, the validity of the model is at least questionable. Animal experiments have repeatedly been conducted addressing the same question, often with striking discrepancies in outcome. Animal studies were even performed after a surgical technique had been pioneered in humans. The use of animal models in urinary diversion is far from standardized rendering the results less than ideal for comparison across studies. Due to differences in anatomy and physiology, the applicability of findings in animal experiments to clinical urology is limited. Continued effort is needed to optimise the use of animal models in experimental urology.

Evaluation of bone mineral density after ileocystoplasty in children with and without myelomeningocele

We evaluated the bone mineral density (BMD) after ileal augmentation cystoplasty in a group of children with and without myelomeningocele. Between 1996 and 2003, eight patients with neurogenic bladder and seven patients with non-neurogenic bladder underwent augmentation ileocystoplasty. Preoperative and postoperative serum creatinine and electrolytes were measured. All patients underwent clinical evaluation, supine height measurement, blood gas analysis, and BMD measurement using a dual energy X-ray absorptiometry (DEXA) postoperatively. BMD was measured at L1-L4 and femoral neck, and compared to age- and sex-matched population. Follow-up time was calculated from the day of surgery to the day of DEXA performance. A total of eight boys and seven girls with the mean age of 10.2 +/- 4.1 years were evaluated with respect to BMD measurement. Mean age was 9.8 years in neurogenic group and 10.5 in non-neurogenic group. Mean follow-up was 728 and 616 days in neurogenic and non-neurogenic groups, respectively. There were no significant differences between ages, follow-up times, preoperative and postoperative creatinine levels, pH and bicarbonate values, and supine heights. Mean BMD at L1-L4 was 55.7% in neurogenic group and 83.8% in non-neurogenic group. There was a statistically significant difference between the two groups (P = 0.02). Mean BMD at femoral neck was 72% in neurogenic group and 86.2% in non-neurogenic group. The difference was also statistically significant (P = 0.028). After augmentation ileocystoplasty, the BMD in early postoperative period of patients with myelomeningocele is lower than the patients with non-neurogenic neurogenic bladder, which have the same clinical characteristics except the neurologic pathology. In the light of our findings and the reported literature data as well, we may claim that BMD decrease after augmentation ileocystoplasty depends more on the underlying neurologic pathology and its locomotor consequences rather than the enterocystoplasty itself.

Bladder, bowel and bones--skeletal changes after intestinal urinary diversion

Impaired bone metabolism following urinary diversion through intestinal segments has always been a controversial subject of unclear clinical relevance. Whereas the perpetuated pathophysiological considerations seem conclusive in theory, the role of acidosis and malabsorption is less clear in animal experimentation and, even more so, in the clinical reality of modern continent diversion. In hardly any of the available contemporary case series was overt derangement of the acid-base balance, rickets or osteomalacia encountered. No consistent changes in osteotropic serum parameters could be found with normal calcium and phosphate in all patients. The assumption that colonic reservoirs have a higher risk of developing metabolic bone disease could not be confirmed by clinical data. As early correction of base excess is easy and probably a common policy in patients with intestinal urinary reservoirs, it will be virtually impossible to further study the natural history of bone metabolism after urinary diversion. While there is no need for a bone specific follow-up in asymptomatic adults with a normal acid-base balance, particular attention should be paid to children and to all patients with impaired renal function.

Effect of Augmentation Cystoplasty on Bone Metabolism in Chronic Uremic Rats

PURPOSE

We examined the impact of urinary diversion using several types of intestinal segments on the bone metabolism of growing rats with renal insufficiency.

MATERIALS AND METHODS

A total of 110, 8-week-old Sprague-Dawley rats underwent 2-stage subtotal nephrectomy by removal of 5/6 of the renal mass or sham operation. Except for a uremic control group all uremic rats underwent enterocystoplasty using stomach, ileum or colon. An additional group with colic augmentation received the bisphosphonate ibandronate. Bone mineral density of the tibia and lumbar spine, serum analysis and urinary excretion of the bone resorption marker deoxypyridinoline were determined monthly for 12 weeks. At study termination bone ash weight, bone mineral analysis and serum osteotropic hormone levels were determined.

RESULTS

All groups undergoing subtotal nephrectomy had a decreased endogenous creatinine clearance of approximately 30%. The lowest gains in tibial and lumbar spine bone mineral density were observed in animals undergoing ileocystoplasty. Femoral calcium content was significantly decreased in uremic ileocystoplasty rats compared with uremic controls. These changes were not induced by alterations in serum pH, nor were they associated with accelerated bone resorption as assessed by deoxypyridinoline. Ibandronate prevented changes related to bone resorption and increased bone mass.

CONCLUSIONS

Our results suggest that cystoplasty using ileum segments can aggravate renal bone disease in growing rats with mild uremia. Since the acid-base state was unchanged, other properties of the interposed ileum segment must be responsible for the negative effect on bone metabolism.

Metabolic Evaluation of 94 Patients 5 to 16 Years After Ileocecal Pouch (Mainz Pouch 1) Continent Urinary Diversion

PURPOSE In continent urinary diversion metabolic disturbances may be encountered in long-term followup. We evaluated metabolic consequences in patients with a minimum followup of 5 years after Mainz pouch 1 urinary diversion.

MATERIALS AND METHODS

At our institution continent urinary diversion using the ileocecal segment was performed between 1983 and 1995 in 458 patients. A total of 94 patients with an ileocecal pouch for a minimum of 5 years were reevaluated for metabolic changes. Median followup was 9.0 years. Routine laboratory parameters, blood gas analysis, vitamin B12, vitamin D25, cross-laps, bone specific alkaline phosphatase, osteocalcin and propeptide of type I collagen were obtained. Bone density was measured in 18 patients. Vitamin B12 changes could be followed longitudinally in 24 patients.

RESULTS

Medians of all parameters were in normal ranges. Clinical examinations revealed no signs of megaloblastic anemia, funicular myelosis or osteoporosis. There was no significant decrease of vitamin B12 in the long run. After followup examination we recommended vitamin B12 supplementation in 32% of patients because levels were in the lower normal range or below. A total of 37% of patients continue to take Na+/K+-citrate for prevention of metabolic acidosis.

CONCLUSIONS

Patients with an ileocecal pouch and a followup of more than 5 years did not present with clinical symptoms caused by metabolic disturbances. Nevertheless, systematic followup of blood gases in particular and alkali supplementation may have prevented bone demineralization. Followup of vitamin B12 is of concern because about a third of these patients need supplementation.

The effect of enterocystoplasty on bone strength assessed at four different skeletal sites in a rat model

The objective of the study was to investigate bone strength at four different skeletal sites in a chronic animal model of urinary diversion. Young male Wistar rats (120) were allocated randomly to four groups undergoing ileocystoplasty; ileocystoplasty and resection of the ileocecal segment; colocystoplasty; or sham operation (controls). After 8 months the lumbar vertebrae, femora, and tibiae were harvested at necropsy. Bone strength was assessed biomechanically at four different skeletal sites: vertebra L3, femoral middiaphysis, femoral neck, and distal femoral metaphysis. Bone mass and architecture were assessed using standard static histomorphometry of the proximal tibial metaphysis (trabecular bone volume [BV/TV]; trabecular number [Tb.N]) and ash weight. Statistically significant differences of biomechanical parameters between groups were observed at three skeletal sites with corresponding changes in tibial histomorphometry. Isolated ileocystoplasty resulted in decreased maximum load values of L3 (-16.4%; p < 0.0035) and a substantial reduction in tibial BV/TV (-34.7%; p < 0.05). Ileocystoplasty combined with resection of the ileocecal segment led to a significant loss of bone strength of L3 (-32.4%; p < 0.0015) and a dramatic reduction of tibial BV/TV (-45.9%; p < 0.01). Loss of tibial metaphyseal bone mass was predominantly caused by a decrease in Tb.N. (p < 0.01). Colonic augmentation had no significant effect on bone strength or histomorphometric values. In conclusion, this is the first experimental study to demonstrate the relevance of histomorphometrically proven bone loss after enterocystoplasty in terms of biomechanical variables.

Skeletal growth and long-term bone turnover after enterocystoplasty in a chronic rat model

OBJECTIVE

To investigate skeletal growth and bone metabolism in a chronic animal model of urinary diversion.

MATERIALS AND METHODS

Young male Wistar rats (120) were allocated randomly to four groups undergoing: ileocystoplasty, ileocystoplasty and resection of the ileocaecal segment, colocystoplasty, and controls. All animals received antibiotics for 1 week after surgery; half of each group remained on oral antibiotics. Bone-related biochemistry was measured in serum and urine. Dual-energy X-ray absorptiometry and peripheral quantitative computed tomography (pQCT) were used to determine bone mass ex vivo.

RESULTS

Most (90%) of the rats survived the study period (8 months); six rats died from bowel obstruction at the level of the entero-anastomosis and four had to be killed because of persistent severe diarrhoea. Vital intestinal mucosa was found in all augmented bladders. There were no differences in bone length and volume. Loss of bone mass was almost exclusively in rats with ileocystoplasty and resection of the ileocaecal segment (-37.5%, pQCT, P < 0.01). There was no hyperchloraemic metabolic acidosis or gross impairment of renal function. Hypomagnesaemia, hypocalcaemia and decreased insulin-like growth factor-binding protein 3 were the only significant findings on blood analysis. Deoxypyridinoline crosslinks in urine were higher in rats with an enterocystoplasty than in controls.

CONCLUSIONS

Enterocystoplasty in rats neither impairs skeletal growth nor bone quantity, but leads to significant loss of bone mass when combined with resection of the ileocaecal segment. Rarefaction of the trabecular network is confined to the metabolically highly active cancellous compartment, most likely as a consequence of intestinal malabsorption.

Evaluation of bone mineral density with dual x-ray absorptiometry for osteoporosis in children with bladder augmentation

BACKGROUND/PURPOSE

Osteoporosis can appear as a result of metabolic acidosis in patients with bladder augmentation and total bladder replacement. These patients must be monitored for early diagnosis and osteoporosis to avoid related complications such as fracture. The current method for diagnosis of osteoporosis mainly involves bone densitometry. Dual x-ray absorptiometry (DXA) provides bone mineral content and bone mineral density (BMD). The purpose of this report is to determine the value of BMD measurement with DXA in the diagnosis and follow-up of osteoporosis and evaluation of response to treatment in the patients with bladder augmentation and total bladder replacement.

METHODS

Six patients with bladder extrophy and neurogenic bladder underwent colocystoplasty, ureterocystoplasty, and total bladder replacement. The Sigmoid colon segment was used for colocystoplasty. DXA (Hologic 2000 DXA) was used for measuring bone mineral content and density. Results for lumbar spinal BMD were expressed as the average of L1 through L4 values. Each patient's BMD was compared with the mean BMD in the young normal population (T score) and in the age- and sex-matched group (Z score). But because our patients were children, BMD was evaluated according to Z score. Arterial blood gas analysis was obtained periodically with BMD measurement. Arterial blood pH and HCO(3) levels of the patients were compared with normal values, which ranged from 7.35 to 7.45 for pH and from 22 to 27 mmol/L for HCO3.

RESULTS

Arterial blood pH of 5 of 6 patients (83.3%) and HCO3 levels of all patients were low. Ten BMD measurements were obtained for 6 children. One patient underwent BMD measurement 3 times, 2 patients underwent twice, and the others once. Z scores of 4 of 6 patients (66.6%) were decreased. Blood pH, HCO3 level, and BMD of 2 patients increased after oral bicarbonate intake. Two patients had normal BMD. One of these patients had ureterocystoplasty. The other had undergone colocystoplasty but was incontinent.

CONCLUSIONS

Intestinal segments have been used for bladder augmentation and total bladder replacement. Exposure of highly absorptive intestinal mucosa to urine has been associated with electrolyte abnormalities and metabolic acidosis. Hyperchloremic acidosis leads to bone demineralization. DXA provides bone mineral content and BMD for diagnosis of osteoporosis. DXA is preferred because the low radiation dose (average, 2 to 4 mrem), accuracy, low price, and short examination time. Not only can BMD confirm the diagnosis of osteoporosis, but it also can be used to monitor the course of the disease and the effectiveness of treatment.

Growth and metabolic consequences of bladder augmentation in children with myelomeningocele and bladder exstrophy

OBJECTIVE

Bladder augmentation using intestinal segments is reported to cause decreased linear growth in bladder exstrophy and myelomeningocele patients. We studied changes in calcium metabolism, height, bone chemistry, and bone density in exstrophy and myelomeningocele patients after bladder augmentation.

METHODS

Thirty-three patients were prospectively admitted to the Pediatric Clinical Research Center at the University of California San Francisco for 24 hours. Blood and urine were analyzed for electrolytes, and serum was obtained for markers of calcium metabolism. Dual radiograph bone densitometry of the forearm was performed. Myelomeningocele patients were compared with nonaugmented myelomeningocele patients matched by age, gender, level of defect, and ambulatory status. Exstrophy augmented patients were compared with nonaugmented exstrophy patients. The bone densities in both groups were compared with normal children. Laboratory values and percentile heights were statistically analyzed using the Student t test; bone densitometry was analyzed using the Tukey test.

RESULTS

Twenty-two patients with myelomeningocele and 11 with bladder exstrophy were studied. Mean follow-up was 3.7 years postaugmentation (range: 1-13 years). The results indicate a significant difference in serum bicarbonate and chloride levels between myelomeningocele patients who underwent ileal augmentation and those who did not. Although this may be indicative of chronic metabolic acidosis, there was no affect on growth or bone density when compared with controls. There were no other significant differences in laboratory values, or percentile heights, nor were any differences noted in patients who underwent gastrocystoplasty. In the exstrophy group, there were no observable differences in percentile height or laboratory values between the augmented and nonaugmented group. There were no significant differences in bone density between these 2 groups when matched for age and gender. No significant difference was seen in bone density when these groups were compared with normal children.

CONCLUSION

Bladder augmentation is safe and does not impact negatively on the linear growth or bone densities of patients with myelomeningocele or bladder exstrophy.

Bone mineral content and related biochemical variables in patients with ileal bladder substitution and colonic Indiana pouch

OBJECTIVES

To evaluate the effects of ileal bladder substitution or colonic Indiana pouch on skeletal bone density and various biochemical parameters related to bone metabolism.

PATIENTS AND METHODS

In 27 patients with urinary diversion and 14 controls with benign urologic disease, bone mineral density (BMD), assessed by dual-photon absorptiometry; serum electrolyte, creatinine, alkaline phosphatase and parathyroid hormone levels were determined, and capillary blood gas analysed. BMD was measured in the lumbar spine and the femur neck. The mean time since surgery was 33.6+/-10.1 months in 17 patients with an ileal bladder substitution and 56+/-9.1 months in 10 patients with a colonic Indiana pouch (p=0.001).

RESULTS

Although BMD did not change in the colonic Indiana pouch group, it was reduced in the patients with ileal bladder substitution compared to control group. The mean pH value was not statistically significant different in the both groups from the control group (p>0.2). The mean base excess value reduced in the substitution group (p<0.01). While alkaline phosphatase levels increased in both groups compared to control group (p<0.05), the mean parathyroid hormone level decreased only in the patients with ileal bladder substitution (p<0.05). The other biochemical parameters were similar in patients and control subjects. There was a statistically significant correlation between the base excess values and BMD values of the patients in both groups.

CONCLUSION

Although there is decreased BMD in patients with an ileal bladder substitute, there is no change in BMD in the patients with Indiana pouch. Alkaline phosphatase levels increased in both patient groups indicating increased bone turnover.

Decreased linear growth associated with intestinal bladder augmentation in children with bladder exstrophy

PURPOSE

We determine if enterocystoplasty results in delayed linear growth using a case controlled study to observe the effects of intestinal bladder augmentation on growth in patients with bladder exstrophy.

MATERIALS AND METHODS

A total of 50 patients who had undergone bladder augmentation for incontinence due to classic bladder exstrophy were selected from our patient database and matched for gender, age and type of exstrophy with 50 patients who had nonaugmented bladder exstrophy. Patients were then contacted and asked to permit the pediatricians to release growth charts. Once consent was obtained the charts were requested from the pediatricians, and evaluable data, defined as at least 1 height before and after augmentation, were obtained for 17 of 50 (34%) augmented and 15 of 50 (30%) nonaugmented cases.

RESULTS

Mean age at surgery was 7.7 years. Delayed growth as defined by a postoperative decrease in percentile height occurred in 14 of 17 (82%) augmented cases (mean loss 15.6 percentile points). Delayed growth after age 7.7 years occurred in 5 of 15 (33%) controls but average growth for the entire group was 6.7 percentile points (p = 0. 014). Mean followup was 5.7 years (median 4.9) for the augmented group and 7.3 years (median 8.2) for the control group.

CONCLUSIONS

Intestinal bladder augmentation is associated with a nearly universal decrease in percentile height. Close long-term followup of these patients and analysis of subtle metabolic alterations may provide information to help minimize or prevent growth impediment in the future.

Orthotopic bladder augmentation and substitution

Orthotopic bladder augmentation or substitution using intestinal segments has become a standard procedure for many disorders that cause a loss of functional or anatomical bladder capacity. From the technical point of view, reservoir configuration by detubularizing the intestinal segments is the general practice. Various techniques exist, depending which types of segments and which techniques of ureteral implantation are used. Common problems include urinary incontinence, retention, metabolic disorders, and the possibility of secondary malignancies. As a result, research has been conducted into utilizing tissues other than intestine for bladder augmentation or substitution.

Whole-body potassium and bone mineral density up to 30 years after urinary diversion

OBJECTIVES

To evaluate the long-term effects of different types of urinary diversion on skeletal bone density and whole-body potassium content in patients with an early correction of base excess (< -2.5).

PATIENTS AND METHODS

The early correction of base excess (< -2.5) is one of the principles of the treatment of patients undergoing urinary diversion at our institution. In 27 patients with urinary diversion, bone mineral density (assessed by dual-photon absorptiometry), whole-body potassium, electrolyte and creatinine levels were determined, and capillary blood gas analysed. The mean time since surgery was 16.8 years in 16 patients with a rectal reservoir, 20.5 years in six patients with a colonic conduit, 7.8 years in four patients with an ileocaecal pouch and 5 years in one adolescent with an ileal bladder augmentation.

RESULTS

Bone mineral density was normal in 25 of the 27 patients; no exact measurement was possible in the remaining two. The whole-body potassium content was reduced in eight of the 27 patients (three with a conduit, two with a rectal reservoir, two with an ileocaecal pouch and one with ileal augmentation). In four of these eight patients the base excess was < -2.5 (-2.7 to -5). Of the other four, two had no regular testing of their base balance and two were obese. The electrolytes were within the normal ranges. None of the patients had hyperchloraemic metabolic acidosis.

CONCLUSION

With early correction of the base excess (< -2.5), there was no decrease in bone mineral density and no hyperchloraemic acidosis. There was no significant difference between the different types of urinary diversion. There seems to be a relationship between low base excess and decreased whole-body potassium.