Changes in whole body potassium associated with uretero-intestinal anastomoses

Metabolic changes after urinary diversion

Urinary diversion is performed on a regular basis in urological practice. Surgeons tend to underestimate the metabolic effects of any type of diversion. From the patient's perspective, diarrhea is the most bothersome complaint after urinary diversion. This might be accompanied by malabsorption syndromes, such as vitamin B12 deficiency. Electrolyte abnormalities can occur frequently such as hyperchloremic metabolic acidosis, or less frequently such as hypokalemia, hypocalcaemia, and hypomagnesaemia. Bone health is at risk in patients with urinary diversion. Some patients might benefit from vitamin D and calcium supplementation. Many patients are also subject to urinary calculus formation, both at the level of the upper urinary tract as in intestinal reservoirs. Urinary diversion can affect hepatic metabolism, certainly in the presence of urea-splitting bacteria. The kidney function has to be monitored prior to and lifelong after urinary diversion. Screening for reversible causes of renal deterioration is an integral part of the followup.

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.

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.

Urinary pH and urea concentration correlate to the bacterial colonization rate in gastric, colonic, ileal and myoperitoneal bladder augmentation

We investigated how various types of augmentation cystoplasty alter the native bacteriostatic properties of urine, particularly urinary urea and pH, in the Sprague-Dawley rat. The augmentation cystoplasties studied included 1 cm.2 and 2 cm.2 patches of colon, ileum and stomach as well as myoperitoneal bladder flaps. Augmentations in order of decreasing incidence of bacteriuria and urinary pH are 2 cm.2 ileal greater than 1 cm.2 ileal greater than 2 cm.2 colonic greater than 1 cm.2 colonic greater than myoperitoneal greater than cystotomy alone greater than 1 cm.2 gastric greater than 2 cm.2 gastric. Urinary urea concentrations were similar between cystotomy alone, and myoperitoneal and gastric augments. In contrast, all colonic and ileal augments had significantly lower urea concentrations compared to the aforementioned groups. Our findings suggest that the type and size of augmentation directly affect urinary pH and urea nitrogen concentration, and the incidence of bacteriuria.

Pathophysiology of potassium absorption and secretion by the human intestine

When normal people ingest 90 mEq/day of K+ in their diet, they absorb about 90% of intake (81 mEq) and excrete an equivalent amount of K+ in the urine. Normal fecal K+ excretion averages about 9 mEq/day. The vast majority of intestinal K+ absorption occurs in the small intestine; the contribution of the normal colon to net K+ absorption and secretion is trivial. K+ is absorbed or secreted mainly by passive mechanisms; the rectum and perhaps the sigmoid colon have the capacity to actively secrete K+, but the quantitative and physiological significance of this active secretion is uncertain. Hyperaldosteronism increases fecal K+ excretion by about 3 mEq/day in people with otherwise normal intestinal tracts. Cation exchange resin by mouth can increase fecal K+ excretion to 40 mEq/day. The absorptive mechanisms of K+ are not disturbed by diarrhea per se, but fecal K+ losses are increased in diarrheal diseases by unabsorbed anions (which obligate K+), by electrochemical gradients secondary to active chloride secretion, and probably by secondary hyperaldosteronism. In diarrhea, total body K+ can be reduced by two mechanisms: loss of muscle mass because of malnutrition and reduced net absorption of K+; only the latter causes hypokalemia. Balance studies in patients with diarrhea are exceedingly rare, but available data emphasize an important role for dietary K+ intake, renal K+ excretion, and fecal K+ losses in determining whether or not a patient develops hypokalemia. The paradoxical negative K+ balance induced by ureterosigmoid anastomosis is described. The concept that fecal K+ excretion is markedly elevated in patients with uremia as an intestinal adaptation to prevent hyperkalemia is analyzed; we conclude that the data do not convincingly show the existence of a major intestinal adaptive response to chronic renal failure.

Urinary solute transport by intestinal segments: a comparative study of ileum and colon in rats

This study was conducted to quantitate and compare urinary solute transport by ileum and colon in an in vivo rat model. Rates of solute transport were compared by analysis of rate constants for each experiment. Sodium and bicarbonate are secreted while ammonium and chloride are absorbed by both ileum and colon. Potassium is absorbed by ileum and not transported by colon. There is a tendency for water movement into the bowel lumen with both intestinal segments. Quantitatively, the amount of bicarbonate secretion and the increase in intraluminal pH is greater with ileum than colon. There is a net osmolar absorption from ileum but not colon. Hydrogen ion or ammonium absorption accounts for the majority and bicarbonate secretion the minority of the acid load in both ileum and colon. Ammonium appears to be absorbed either along with chloride or in exchange for sodium.

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.

Study on use of isolated segment of ileum in urological plastic operation

Studies were done on 33 cases of plastic reconstruction of the urinary tract with an isolated ileal segment. We found that electrolytes and other components in the urine can be absorbed or excreted by the isolated ileal mucosa. Although electrolyte balance was preserved in most cases the tendency for hyperchloremic acidosis and high blood urea nitrogen was observed in some patients with poor renal function. The degree and the incidence of these changes were influenced by the length of ileal segment used and the volume of urine excreted. These 2 factors were related to infection, which gave deleterious effects on renal function. Among the tests used for prognosis the excretory urogram was found to be the most simple and provided the best information.

Whole body potassium in patients with ureterosigmoid anastomoses

Total body potassium was measured by whole body counting in 11 patients with uretero-sigmoid anastomoses who had undergone cystectomy 4 months to 13 years previously. The measured total body potassium was not significantly different in any of the patients from the "normal" value for the individual patients, predicted from height and age. It was only significantly different from that predicted from height, age and weight in 1 patient. In the series as a whole, the measured values of whole body potassium were not significantly different from the "normal" values estimated by either relationship. From measurements of skinfold thickness, the lean body mass of each patient was estimated. The mean potassium content, 62-0 mEg/kg LBM in the male patients was within the normal range. The absence of potassium depletion may derive from the successful abolition of hyperchloraemic acidosis by long-term alkali therapy.