Diverse patterns of acid-base abnormalities associated with a modified sigmoid neobladder

In this study, we analyzed the pattern of metabolic acidosis in patients following the construction of a sigmoid neobladder and then search for the risk factors which affecting this. In 23 men aged 43-73 years and nine women aged 49-74 years who underwent sigmoid neobladder surgery, we performed physical examinations and blood tests every 3 months for 13-75 months (38.7+/-16.6: mean+/-SD). We monitored acid-base balance, serum electrolytes, creatinine, lipid and liver function in patients for up to 6 years postoperatively. Creatinine clearance over 24 h was determined preoperatively. According to pH and base excess measured during follow-up, patients were classified into three groups (normal, 17 patients; temporary acidosis, eight patients; persistent acidosis, seven patients). Patients with temporary acidosis could compensate spontaneously by 1 year without being given sodium bicarbonate; those with persistent acidosis could not compensate spontaneously and five of them required medication with sodium bicarbonate after 1 year. Serum creatinine in patients with persistent acidosis was consistently higher during follow-up than in the other two groups. Preoperative creatinine clearances in the normal, temporary, and persistent groups were 94.25+/-27.47, 95.19+/-18.63, and 69.18+/-16.18 ml/min/1.73 m(2), respectively, being significantly lower in the persistent group ( P<0.05). In this group, patients with creatinine clearances less than 70 ml/min/1.73 m(2) could not compensate for metabolic acidosis. Normal and temporary groups showed different changes of serum chloride and bicarbonate during follow-up (respectively higher and lower) although the renal functions of the two groups were similar. Chloride and bicarbonate varied reciprocally with pH and base excess. Temporal hyperchloremic metabolic acidosis was observed until a year after surgery. In conclusion, temporary acidosis can be caused in some patients in spite of normal renal function, although it is difficult to predict it. In addition, careful follow-up is required, especially in patients with a creatinine clearance <70 ml/min/1.73 m(2) who can encounter persistent acidosis.