Excessive sac pressures: the pathogenesis and innocence of hydroceles in children

Objective To determine whether paediatric hydroceles result entirely from a small-calibre patent processus vaginalis, allowing free communication between the abdominal cavity and hydrocele sac, or whether there are other mechanisms. Patients and methods Twenty-five hydroceles were studied prospectively in 24 boys (aged 18–132 months). Consent for the intraoperative measurements was obtained before surgery. The hydrocele was repaired under general anaesthesia with endotracheal intubation, using a standard approach, taking care not to open the sac during mobilization. Intra-abdominal pressures during surgery were measured indirectly via a nasogastric tube after gastric decompression. The pressure in the sac was measured via a 20 G intravenous cannula inserted via a purse-string suture. The relative pressure was then calculated by subtracting the intra-abdominal from the sac pressure. The effects of age and laterality were evaluated. Results The median (range) intra-abdominal, sac and relative pressures were 8 (2–18), 11 (3–30) and 4 (3–30) cmH2O, respectively. The sac pressure in the sac was greater than the intra-abdominal pressure in 17 of 25 (68%; P = 0.004) patients. Age or laterality had no significant influence on any of the pressures. Conclusions These results suggest that in a significant proportion of hydroceles in children the pressures are higher than the intra-abdominal pressure. Therefore, they cannot be explained simply as a freely communicating, narrow-calibre processus. In addition, the pressures may reach levels which are potentially damaging to the testis.