Diurnal Patterns of Urinary Excretion during Polyuria after Pituitary Surgery and Its Management

Abstract

Polyuria following pituitary surgery (removal of the adenomas, hypophysectomy and neuroadenolysis) was studied in 64 cases. Most of the postoperative polyuria were diabetes insipidus showing Randall's triphasic pattern and disappeared within 6 months. A successive observation of hourly urinary volume was carried out, and four patterns of diurnal excretion were classified. The continuous pattern, continuously sustained polyuria, was observed in the 1st postoperative day when polyuria started within 6 hrs after pituitary surgery. It was commonly followed by a rhythmic pattern after the 2nd postoperative day. The rhythmic pattern showed one to three peaks in which an abrupt increase in hourly urinary volume at constant clock time was demonstrated. This pattern was observed following pituitary surgery and in idiopathic diabetes insipidus. Intermittently administered pitressin and inadequate drip infusion of electrolyte solution often affected the rhythmic pattern, resulting in appearance of false peaks, and the genuine peaks revived when the inapproprate treatment were corrected. A transient pattern was observed in the polyuria which disappeared within a day. This pattern was also seen in the pnlyuria induced by diuretics administered in the postoperative stage of surgery other than pituitary surgery.
A unspecific pattern was shown during recovery stage of the postoperative polyuria with the rhythmic pattern. It was also seen in the acute stage following the pituitary surgery when inadequate drip infusion and/or a overdose of sodium were given, and was frequently accompanied by a gain in body weight. Free water clearance was constantly increased at the time of the peaks in the rhythmic pattern. The mechanism through which the diurnal patterns of polyuria were induced still remained to be determined, but it was assumed that surgical intervention on the pituitary gland would decrease ADH secretion and suppress the diurnal change.
In the management of the polyuria following pituitary surgery, checking for the diurnal pattern of urinary excretion had many advantages in terms of simplicity of procedure to differentiate the nature of polyuria, excluding inappropriate treatment and predicting the prognosis. Rectal administration of indomethacin suppositories was recommended for the reduction of urinary volume in the acute postoperative stage without affecting the diurnal patterns of polyuria following pituitary surgery.