Symptomatic renal obstruction or urosepsis during pregnancy: treatment by sonographically guided percutaneous nephrostomy. 
Seven pregnant women with symptomatic hydronephrosis had sonographically guided percutaneous nephrostomy for pyosepsis (five patients) or for pain with azotemia (two patients with renal transplants).  Antibiotics had been ineffective in controlling pyosepsis in each patient; retrograde ureteral catheterization via cystoscopy was unsuccessful in one patient.  After percutaneous nephrostomy, prompt clinical improvement was observed in all patients (i.e., sepsis was relieved and pain abated).  Labor was not induced in any of the patients, and no adverse effects occurred to any fetus or mother.  Eleven (eight percutaneous nephrostomy, three catheter exchanges) of the 12 procedures were done without conventional radiography and with sonographic guidance alone.  After percutaneous nephrostomy, maneuvers to obtain a diagnosis and to treat the obstruction (if necessary) were delayed until after delivery.  The causes of ureteral obstruction were calculi (four patients) and a gravid uterus (three patients).  After delivery, stones were removed either percutaneously (one patient) or cystoscopically (two patients) or passed spontaneously (one patient); resolution of obstruction by the gravid uterus was proved by Whitaker test after delivery.  Sonographically guided percutaneous nephrostomy is an effective and safe method to treat pregnant women who have symptomatic obstructive hydronephrosis associated with either pyosepsis or azotemia.  The procedure is rapid, requires minimal anesthesia, has no radiation, and is safe for the fetus.  The technique is a useful and perhaps preferable alternative to more invasive surgical therapy or retrograde stenting.