The osteomalacia syndrome after colocystoplasty; a cure with sodium bicarbonate alone

Update on bone fragility in spina bifida

BACKGROUND CONTEXT

Patients with spina bifida (SB) are at risk for pathological fractures and low bone mineral density (BMD).

PURPOSE AND METHODS

This article reviews the literature and provides a comprehensive overview of how the characteristics of SB and its associated comorbidities intersect with bone fragility to identify possible pathophysiological mechanisms of fractures and low BMD.

RESULTS

Bone fragility occurs early in the life of patients with SB as a result of a disturbance that determines changes in bone shape, quantity, and quality, as poor mineralization reduces bone stiffness. Bone fragility in SB occurs due to local and systemic factors and may be considered a state of impaired bone quality of multifactorial aetiology, with complex interacting influences of neurological, metabolic, and endocrinological origins and the presence of smaller bones. Bone fragility should be evaluated globally according to skeletal age and Tanner staging. The phases of the evolution of Charcot joints seem to intercept the evolution of epiphyseal fractures. Charcot arthropathy in SB may be initiated by the occurrence of repetitive trauma and fractures in epiphyseal and subepiphyseal regions, where there is a deficit of bone mineralization and greater bone mass deficits.

CONCLUSION

Bone fragility in MMC potentially has a multifactorial neuro-endocrinological-metabolic-renal dimension, with smaller bones, lower bone mass, and mineralization deficits affecting bone strength.

OSTEOMALACIA AS A RESULT OF URINARY DIVERSION

A 54 years old man, who had undergone a cystectomy and urinary diversion surgery 31 years previously, complained of progressive generalized bone pain, muscle weakness and walking abnormality for six months. Laboratory investigations revealed elevated alkaline phosphatase, high serum chloride level and metabolic acidosis. Osteomalacia was suspected due to clinical and laboratory findings. Osteomalacia due to hyperchloremic metabolic acidosis is a complication of urinary diversion. Regular monitoring of pH, chloride, bicarbonate, and calcium-phosphorus metabolism is therefore essential for early diagnosis and treatment.

Metabolic consequences after urinary diversion

Metabolic disturbances are well-known, but sometimes neglected immediate consequences or late sequelae following urinary diversion (UD) using bowel segments. Whereas subclinical disturbances appear to be quite common, clinically relevant metabolic complications, however, are rare. Exclusion of bowel segments for UD results in loss of absorptive surface for its physiological function. Previous studies demonstrated that at least some of the absorptive and secreting properties of the bowel are preserved when exposed to urine. For each bowel segment typical consequences and complications have been reported. The use of ileal and/or colonic segments may result in hyperchloremic metabolic acidosis, which can be prevented if prophylactic treatment with alkali supplementation is started early. The resection of ileal segments may be responsible for malabsorption of vitamin B12 and bile acids with subsequent neurological and hematological late sequelae as well as potential worsening of the patient's bowel habits. Hence, careful patient and procedure selection, meticulous long-term follow-up, and prophylactic treatment of subclinical acidosis is of paramount importance in the prevention of true metabolic complications.

[Metabolic long-term complications after urinary diversion]

Metabolic long-term complications and consequences after urinary diversion are somewhat neglected. Subclinical metabolic disturbances are quite common; however, complications are rare. The absorptive surface of the bowel segment is lost for the physiological function of the gastrointestinal tract. Some studies demonstrated that at least some of the absorbent and secreting properties of the bowel are preserved if exposed to urine. For each bowel segment typical complications are reported. Using ileal and/or colon segments, hyperchloremic metabolic acidosis may occur. Studies demonstrated that metabolic effects are not as severe as suspected and could be prevented if a prophylactic treatment is started early.The resection of ileal segments is responsible for malabsorption of vitamin B(12) and bile acid; when using colonic segments, electrolyte disturbances are more common. Careful patient selection, meticulous follow-up and prophylactic treatment are crucial to prevent metabolic complications.

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.

Osteomalacia due to a bladder reconstruction performed 35 years previously

We report a 54-year-old man with osteomalacia due to a bladder reconstruction performed 35 years previously. He had had slowly progressive chest and back pain for 18 months. Osteomalacia due to metabolic acidosis was suspected based on hyperalkalinephosphatasemia and a high serum chloride level, and the diagnosis was confirmed by bone scintigraphy. His symptoms and blood electrolyte levels were improved by oral medication, including sodium hydrogen carbonate. Measurement of the serum chloride level is simple and useful for evaluating acidosis, for which a regular blood test is essential in patients who have undergone bladder reconstruction.

Urinary Diversion

A consensus conference convened by the World Health Organization (WHO) and the Société Internationale d'Urologie (SIU) met to critically review reports of urinary diversion. The world literature on urinary diversion was identified through a Medline search. Evidence-based recommendations for urinary diversion were prepared with reference to a 4-point scale. Many level 3 and 4 citations, but very few level 2 and no level 1, were noted. This outcome supported the clinical practice pattern. Findings of >300 reviewed citations are summarized. Published reports on urinary diversion rely heavily on expert opinion and single-institution retrospective case series: (1) The frequency distribution of urinary diversions performed by the authors of this report in >7000 patients with cystectomy reflects the current status of urinary diversion after cystectomy for bladder cancer: neobladder, 47%; conduit, 33%; anal diversion, 10%; continent cutaneous diversion, 8%; incontinent cutaneous diversion, 2%; and others, 0.1%. (2) No randomized controlled studies have investigated quality of life (QOL) after radical cystectomy. Such studies are desirable but are probably difficult to conduct. Published evidence does not support an advantage of one type of reconstruction over the others with regard to QOL. An important proposed reason for this is that patients are subjected preoperatively to method-to-patient matching, and thus are prepared for disadvantages associated with different methods. (3) Simple end-to-side, freely refluxing ureterointestinal anastomosis to an afferent limb of a low-pressure orthotopic reconstruction, in combination with regular voiding and close follow-up, is the procedure that results in the lowest overall complication rate. The potential benefit of "conventional" antireflux procedures in combination with orthotopic reconstruction seems outweighed by the higher complication and reoperation rates. The need to prevent reflux in a continent cutaneous reservoir is not significantly debated, and this should be done. (4) Most reconstructive surgeons have abandoned the continent Kock ileal reservoir largely because of the significant complication rate associated with the intussuscepted nipple valve.

Distal Renal Tubular Acidosis: Alkali Heals Osteomalacia and Increases Net Production of 1,25-Dihydroxyvitamin D

In 2 women with distal renal tubular acidosis and osteomalacia, alkali treatment cured the bone disease and was accompanied by marked increases in the serum 1,25 dihydroxyvitamin D concentration, without a significant change in the 25-hydroxyvitamin D concentration.

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.

Metabolic complications of urinary diversions: an overview

Patients with urinary diversions present unique challenges to internists who have an important role in their long-term management. Advances in surgical techniques over the past 30 years have given rise to a number of urinary diversion procedures that use various intestinal segments. In its normal function, the intestine absorbs water and solutes. When placed in contact with the urinary stream, the intestine can create numerous metabolic abnormalities. These include bone disease, hepatobiliary disease, infection, malignancy, neurologic complications, nutritional deficiencies, and a number of electrolyte and acid-base disorders. An overview of these metabolic abnormalities and their causes is provided, as well as recommendations for screening and management of patients.

Osteopenia, bone fragility and reflex sympathetic dystrophy syndrome in a man with ureterosigmoidostomy

A 68-year-old man is presented with a reflex sympathetic dystrophy syndrome (RSDS) of the right ankle diagnosed by radiography, magnetic resonance imaging and bone scintiscan. Investigations, including blood tests and bone biopsy, revealed a diagnosis of metabolic acidosis and osteomalacia. These appeared to result from a ureterosigmoidostomy performed 9 years previously for a transitional carcinoma of the bladder. Correction of the metabolic acidosis coincided with improvement in ankle pain. RSDS may be the initial presentation of osteomalacia, which in turn may be caused by the metabolic acidosis resulting from a ureterosigmoidostomy.

Long-term metabolic effects of urinary diversion on skeletal bone: histomorphometric and mineralogic analysis

OBJECTIVES

To evaluate the long-term influence of different types of intestinal urinary diversion on skeletal bone and its mineral content.

METHODS

Densitometry was used to estimate bone mineral content, and bone biopsies were analyzed with histomorphometric technique. The study comprised 20 patients with conduit urinary diversion and 19 with cecal continent reservoir, all followed up for more than 5 years, with normal or near-normal renal function.

RESULTS

Bone mineral content did not differ significantly between the patients with cecal continent urinary reservoir and those with conduit diversion or between these groups and a reference group. At the cellular level, the histomorphometric analysis revealed no defective bone mineralization or increased bone resorption in either group of patients. The trabecular bone volume was greater than normal in the reservoir group, but not in the conduit group. The appositional rate was significantly below normal in both groups of patients, but did not differ between conduit and reservoir patients.

CONCLUSIONS

Subtle changes in electrolytes and acid-base homeostasis identified in adults with intestinal segments incorporated in the urinary tract and with largely normal renal function do not seem to influence bone mineralization in the long term. At the cellular level, a lower than normal appositional rate was found in the patients with conduit or continent urinary diversion. In the latter group, this finding, together with increased trabecular bone volume, may indicate a decrease of bone turnover.

Long-term metabolic effects of urinary diversion: a comparison of myelomeningocele patients managed by clean intermittent catheterization and urinary diversion

We previously reported that chronic urinary diversion through intestinal segments may have adverse effects on bone and mineral metabolism. This study examined the long-term health of patients managed by urinary diversion (94% by ileal conduit) for neuropathic bladders secondary to myelomeningocele defects and compared them to a control population of myelomeningocele patients managed by intermittent catheterization. Of the patients 93 were studied by personal interview, chart review, morphometric analysis, serum studies and dual-photon bone density determination. Average followup was 23 +/- 6 years in the urinary diversion group and 17 +/- 5 years in the intermittent catheterization group. Fractures occurred in 40% of the patients in both groups. Patients with a urinary diversion had an increased need for surgery to correct spinal curvature (57% versus 40%) and a significantly increased incidence of complications resulting from orthopedic procedures (17% versus 3%, p less than or equal to 0.05). There was also an adverse effect on renal function. The urinary diversion group had an increased incidence of radiographic renal deterioration (57% versus 8%, p less than 0.001), nephrolithiasis (43% versus 2%, p less than 0.001), pyelonephritis (60% versus 21%, p less than 0.001) and intermittent metabolic acidosis (20% versus 5%, p = 0.05). Surgery was required in 37% for stomal complications and in 17% for ureterointestinal stricture. Linear growth was adversely affected by urinary diversion. Patients with urinary diversion had decreased lengths for all morphometric parameters and a greater percentage of them were at or below the 10th percentile standards. Serum electrolytes, liver function studies, vitamin D3 and parahormone showed no differences in the 2 groups. No patient had a significant metabolic acidosis at the time of study. Bone densities were significantly diminished in both groups and not significantly different. This study strongly suggests that urinary diversion through intestinal segments is associated with adverse effects on bone health.

Effect of sulfate on calcium and magnesium homeostasis following urinary diversion

The present investigation was undertaken to elucidate the mechanisms of renal calcium and magnesium wastage in patients with urinary diversion through intestinal segments. Patients with urinary intestinal diversions demonstrated a hyperchloremic metabolic acidosis, increased serum sulfate and phosphate, and increased urinary excretion of calcium, phosphate, sulfate, and magnesium. A study was conducted in rats utilizing oral or intravenous loads of various solutes to investigate the possible mechanisms of these findings in patients. Ammonium enhances renal sulfate excretion and intestinal sulfate absorption. Increased filtered loads of sulfate inhibit renal tubule sodium and calcium reabsorption. Dietary ammonium and sulfate result in increased serum phosphorous concentrations. Ammonium appears to directly inhibit renal magnesium reabsorption. Renal tubule dysfunction resulting from relieved obstruction appears to enhance the inhibitory effect of sulfate on renal sodium and calcium reabsorption but does not alter the effect of ammonium on renal magnesium excretion. Taken together, these findings suggest that patients with hyperchloremic metabolic acidosis from the chronic reabsorption of ammonium chloride by intestinal urinary diversions may also reabsorb urinary sulfate. This load of ammonium and sulfate inhibits renal calcium and magnesium reabsorption.

Bony demineralization following urinary intestinal diversion

The effect of urinary intestinal diversion on bone mineral metabolism was investigated in 78 rats. The animals were divided into sham-operated controls and diverted animals. The diverted animals were given either no supplement, sodium bicarbonate or ascorbic acid for an eight month period. Dual photon densitometry and bone mineral content were determined. Urinary intestinal diversion resulted in a minimal systemic acidosis and little alteration in baseline renal function but a significant decrease in bone calcium content. Oral bicarbonate and ascorbic acid administration prevented the demineralization.

Calcium metabolism of intact and thyroparathyroidectomized rats fed a bicarbonate enriched diet

Rats fed a bicarbonate-enriched diet become alkalotic during their feeding period (ca. 10 h/day). Alkalosis produced a significant reduction in the plasmatic concentration of ionized calcium and increased parathyroid hormone secretion confirmed by concurrent hypophosphatemia and increased urinary excretion of cAMP. Three weeks of treatment produced, however, a significant reduction of bone Ca resorption. The increased endogenous fecal excretion of calcium counteracted the enhancement of true calcium absorption. No significant change in the skeletal calcium mass was observed. Thyroparathyroidectomized rats fed the alkaline diet reduced further their rate of bone Ca resorption and increased significantly their skeletal calcium mass.