Proctocolectomy with ileal pouch-anal anastomosis (IPAA) has become the procedure of choice for many children with ulcerative colitis and familial polyposis. The modified quadruple-limb (W) IPAA was designed to increase reservoir compliance and capacity, and to improve functional results by decreasing stool frequency. However, only limited information has been reported concerning the technical considerations and functional outcomes from W IPAA modification and utilization in the pediatric population. Additionally, pediatric IPAA physiological adaptation, expressed as IPAA volume/pressure relationships, for any type of IPAA design has not been described. In this report, the authors analyze their functional and physiological results with W IPAA in 19 children undergoing colectomy for ulcerative colitis and familial polyposis. Since 1986, 19 children (5 girls, 14 boys; mean age, 15.3 years [range, 11 to 18 years]) have undergone proctocolectomy with W IPAA for ulcerative colitis (n = 9) and familial polyposis (n = 10). IPAA pressure and volume profiles were measured in 10 patients at 2 and 12 months postileostomy takedown, and in five patients at 3 years. W IPAA compliance was calculated as the change in volume over change in pressure ( ΔV ΔP). There were no deaths, anastomotic leaks, or pelvic sepsis. The 24-hour stool frequency (mean ± SEM) decreased significantly (P ≤ .05) from 4.6 ± 0.6 at 2 months to 3.3 ± 0.1 at 12 months. No nighttime evacuation occurred after 12 months. W IPAA evacuation volume significantly increased (P ≤ .05) from 238 ± 22.9 mL at 2 months to 346 ± 26.5 mL at 12 months and remained stable thereafter. Reservoir compliance (12.0 ± 1.1 mL/mm Hg at 2 months, 15.1 ± 1.5 mL/mm Hg at 12 months) did not increase significantly with reservoir adaptation. At 12 months, continence was excellent in all patients except two who reported occasional minimal nighttime seepage. The authors conclude that the W IPAA, modified to outlined pediatric standards, is a viable option for ileal reservoir reconstruction in the pediatric population; it provides excellent functional properties relative to straight ileoanal or non-IPAA procedures, and maintains stable initial and long-term pressure/volume relationship profiles and compliance characteristics necessary for optimal IPAA function. © 1994.