Segmental Absence of Intestinal Musculature in a 64-Year-Old Female: Case Report and Literature Review

Background

Segmental absence of intestinal musculature (SAIM) is a well described entity in the pediatric population, especially premature infants. It is diagnosed based on pathologic examination of the bowel. The presentation of this condition in adults is very rare. To the best of our knowledge, twelve cases of SAIM have been described in adults. Here, we report the thirteenth case of SAIM in a 64-year-old female, and we discuss the clinical and pathologic findings of SAIM in adults.

Case Report

GROSS EXAMINATION:

The hemicolectomy specimen consisted of a 34.5 cm (in length) ×2.0–3.2 cm (in diameter) segment of colon with stapled ends and up to a 4.5 cm portion of attached peri-colonic fat. The colon had a 2.7 cm area of perforation 5.0 cm from the closest stapled margin. Two segments of the colon adjacent to the perforation site had thin wall with loss of the muscular layer (Figure 1). The peri-colonic fat had two small lymph nodes. Sampling of the perforation, colonic wall adjacent to perforation, stapled margins, and lymph nodes was performed. The sampled tissue was then embedded in paraffin and stained with hematoxylin and eosin stain.

MICROSCOPIC EXAMINATION:

The microscopic examination revealed acute inflammation and colonic perforation through a muscular wall defect. There was abrupt loss of muscularis propria in the bowel segment with grossly thinned wall. No thrombosed blood vessel, loss of nerves, or loss of mucosa, submucosa, or serosa was seen. The colonic tissues at the stapled margins were unremarkable. The lymph nodes were reactive (Figures 2–5).

FOLLOW-UP:

The patient tolerated the procedure well and was discharged ten days postoperatively. However, she presented four months later with multiple intraabdominal abscesses and severe inflammation of the small bowel secondary to anastomotic leak. Irrigation and drainage of the abscesses were performed. The anastomotic leak was repaired, and segments of the small and large bowel were resected. Pathologic examination of the resected bowel showed acute and chronic inflammation. No loss of intestinal musculature was noted.

Discussion

In 1997, Darcha et al. described the first case of SAIM in adults in a 64-year-old female, who had iatrogenic sigmoid colon perforation during endoscopic removal of a rectal polyp [1]. A study published by Tamai et al. described seven cases of SAIM in a retrospective study involving patients who presented with spontaneous intestinal perforation [2]. The true incidence of SAIM is not known, as this entity is segmental and the diagnosis requires a high index of suspicion. The disease affects men and women equally. The age range of SAIM in adult is 28–64 years. However, the majority of cases are described in older adults. Clinically, SAIM presents with a sudden episode of intestinal perforation or obstruction. Associated clinical symptoms include severe abdominal pain, fever, nausea, vomiting, and abdominal distention. Perforation can be single or multiple. SAIM is described more frequently in the large intestine than in the small intestine. In adults, no cases have been described in stomach, duodenum, or rectum [1–6]. A summary of the reported cases of SAIM in adults is provided in Table 1.

The pathogenesis of SAIM is not yet understood. Theoretically, the disease can be congenital or acquired [7–9]. Congenital SAIM probably results from defects in embryogenesis. Proposed mechanisms include failure of regression of intestinal diverticula, or over-resorption of muscles during regression of the omphalomesenteric duct during embryogenesis [7]. Some researchers have suggested that SAIM results from transient ischemia secondary to vascular accident during embryogenesis, or secondary to transient intussusception [8]. The ischemia theory might help explain some of the acquired cases of SAIM in adults. Among adults with SAIM, 38% had hypertensive vascular diseases or history of bowel ischemia. Two of the reported cases had mesenteric vessel thrombosis, which was confirmed by microscopic pathology examination of mesentery [4,6]. However, the ischemia theory does not explain SAIM in adults with no vascular diseases. It also does not explain the preservation of the mucosa, which is more sensitive to ischemia than the muscularis propria.

On gross pathology examination, bowel segments with SAIM usually have a very thin, paper-like wall. Other gross features that might be associated with SAIM include perforation, ulceration, and diverticulosis. However, evaluation of bowel wall might be difficult in areas with perforation. Therefore, meticulous gross examination of bowel wall throughout the resected bowel segment is essential. Thinned wall might be easier to appreciate in segments adjacent to the perforated area. On microscopic examination, there will be a gradual or abrupt loss of the circular as well as the longitudinal layer of the muscularis propria. Approximately 50% of cases had loss of nerve plexuses in areas lacking muscularis propria. No loss of mucosa, submucosa, and serosa is associated with this condition. Inflammation and mesenteric vessel thrombosis are unusual [2–6].

Cases with SAIM are usually treated with surgical resection of the involved segment. As the incidence of the disease is not known, it is difficult to predict the prognosis of SAIM. However, no recurrences of intestinal perforation have been reported. Mortality was reported in only one case, in which the patient died two days postoperatively as a result of pulmonary edema [2].

In our case, the patient was a 64-year-old female, the same age and gender as the first reported case of SAIM in adults. The patient did not have evidence of vascular diseases. She presented with spontaneous intestinal perforation and had hemicolectomy. She developed postoperative complications secondary to anastomotic leak, but she did not have a recurrence of intestinal perforation. Microscopic examination of the descending colon showed SAIM and inflammation. No loss of nerves was noted, as opposed to 50% of the described cases.

The patient’s family history of osteogenesis imperfecta made us consider the possibility of undiagnosed underlying connective tissue disease that affected the vascular supply to intestinal musculature. However, we do not have evidence to support that possibility. The etiology of SAIM in this case remains mysterious.

Conclusions

In summary, segmental absence of muscularis propria is a rare entity with unknown etiology. The disease can present in pediatric as well as in adult populations. Thorough gross and microscopic examination of bowel segment is essential for diagnosis. Pathologists should be aware that this entity is segmental and keep a high index of suspicion when evaluating bowel resections, especially in cases of intestinal obstruction or perforation.