ORIGINAL CONTRIBUTIONS Effect of Delivery on Anal Sphincter Morphology and Function Jan Zetterstr6m, M.D.,* Anders Mellgren, M.D., Ph.D.,-~ Linda L. Jensen, R.N.,t W. Douglas Wong, M.D.,t Don G. Kim, M.D.,t Ann C. Lowry, M.D.,t Robert D. Madoff, M.D.,t Susan M. Congilosi, M.D.t From the *Division of Obstetrics and Gynaecology, Karolinska Instituter at Danderyd Hospital, Stockholm, Sweden and tDepartment of Surgery, Division of Colon and Rectal Surgery, University of Minnesota Medical School, St. Paul, Minnesota PURPOSE: Anal sphincter injury is a serious complication of childbirth, which may result in persistent anal inconti- nence. Occult injuries, visualized with endoanal ultrasonog- raphy, have previously been reported in up to 35 percent of females in a British study. The aim of the present study was to study anal sphincter morphology and function before and after delivery in primiparous females in the United States. METHODS: Thirty-eight primiparous patients (mean age, 31 years) were evaluated with endoanal ultrasonography, anal manometry, and pudendal nerve terminal motor latency during pregnancy and after delivery. Bowel function before and after delivery was recorded according to set question- naires. Cesarean section was performed in three patients. RE- SULTS: Clinical sphincter tears, requiring primary repair, oc- curred in 15 percent of the patients. After delivery endoanal ultrasonography revealed disruptions in the external anal sphincter in six patients, but no patient had disruption in the internal anal sphincter. One patient had slight scarring in the external sphincter. Of the seven patients with pathologic find- ings at endoanal ultrasonography, the left pudendal latency increased after delivery (P < 0.05), and manometric results were reduced. Three of these seven patients had a third- degree or fourth-degree tear during delivery. All investigations were normal in the three patients who underwent cesarean section. CONCLUSIONS: The present study demonstrates a significant frequency of sphincter injuries (20 percent) after vaginal delivery. Obstetricians should be aware of this risk and explicitly inquire about incontinence symptoms at follow-up after delivery. [Key words: Sphincter injury; Sphincter disrup- Health East Foundation and Mead Johnson Pharmaceutical Inc. provided economic support, enabling participating volunteers to receive a stipend and baby supplies on completion of their tests. Dr. Mellgren was supported by grants from Health East Foundation and Karolinska Institutet Research Funds. Dr. ZetterstrOm was sup- ported by grants from Karolinska Institutet Research Funds. Read at the meeting of The American Society of Colon and Rectal Surgeons, San Antonio, Texas, May 2 to 7, 1998. Poster presentation at the XVIIth Biennial Congress of the International Society Of University Colon and Rectal Surgeons, Malm6, Sweden, June 7 to 11, 1998. No reprints are available. tion; Delivery; Fecal incontinence; Endoanal ultrasound; Ma- nometry; Pudendal latency] Zetterstr6m J, Mellgren A, Jensen LL, Wong WD, Kim DG, Lowry AC, Madoff RD, Congilosi SM. Effect of delivery on anal sphincter morphology and function. Dis Colon Rectum 1999;42:1253-1260. A nal incontinence is regarded as the "unvoiced symptom, 'u and it is common that affected indi- viduals avoid seeking medical attention. 2 Females are affected by anal incontinence more often than males, with the reason for this difference considered to be childbirth. 3-5 A recent prospective study from the United Kingdom indicated that between 4 and 6 per- cent of patients having vaginal delivery will suffer from fecal incontinence. ~ Vaginal delivery may result in disruption of the anal sphincter muscles, pudendal neuropathy, or both. v, 8 Treatment is tailored according to the underlying pathogenesis and severity of the symptoms. 9<1 The incidence and consequences of recognized sphincter tears during delivery have been investigated in several studies. The incidence is generally less than 3 percent, 12-15 and these injuries are usually repaired surgically at the time of delivery. Recent studies have reported suboptimal outcome in approximately 40 percent of these patients, leading to continued anal incontinence of varying degrees. ~5-~v Sphincter injuries during delivery may, however, be overlooked and result in anal incontinence. The im- pact of unrecognized sphincter injuries is largely un- known. In a recent study Sultan et al. 8 found an incidence of 35 percent occult sphincter injuries in 1253