Adynamic ileus after Caesarean section mimicking

intestinal obstruction: findings on abdominal

radiographs

B F KAMMEN, MD, M S LEVINE, MD, S E RUBESIN, MD and I LAUFER, MD

Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia,

PA 19104, USA

Abstract. The purpose of this study was to determine the spectrum of findings and the frequency

of apparent distal colonic obstruction on abdominal radiographs in women with obstructive

symptoms following Caesarean section. A search of radiology files yielded 21 patients who had

abdominal radiographs because of obstructive symptoms during the early post-operative period.

The radiographs were reviewed retrospectively to characterize the bowel gas patterns in these

patients. Medical records were also reviewed to determine the treatment and patient course.

Abdominal radiographs showed findings suggestive of distal colonic obstruction in 15 patients

(71%), small bowel obstruction in 2 (10%), adynamic ileus in 3 (14%) and a normal bowel gas

pattern in 1 (5%). In all 15 patients with apparent distal colonic obstruction, there was minimal or

no gas in the rectosigmoid, with an associated pelvic mass representing the enlarged post-partum

uterus, which compressed the rectosigmoid and prevented it from filling with gas. All 21 patients

had rapid clinical or radiographic improvement on conservative management, indicating a

transient post-operative ileus. Radiologists should be aware of the limitations of abdominal plain

radiographs following Caesarean section so that a post-operative ileus is not mistaken for a distal

colonic obstruction and conservative measures can be undertaken to decompress the bowel until

the ileus resolves.

It is well known that women who undergoCaesarean section may develop an acute post-operative ileus characterized by transient, occa-sionally severe, colonic dilatation that resolvesspontaneously [17]. We have noticed that thisadynamic ileus is sometimes manifested onabdominal radiographs by marked colonic dilata-tion with minimal or absent gas in the rectosig-moid, mimicking the appearance of a distalcolonic obstruction. We therefore performed aretrospective study of abdominal radiographs inwomen with obstructive symptoms followingCaesarean section to determine the spectrum ofradiographic findings and the frequency ofapparent distal colonic obstruction in thesepatients.

Materials and methods

Approximately 3200 Caesarean sections wereperformed at our hospital during the 8-yearperiod between 19901998. A computerizedsearch of radiology files showed that 26 of thepatients had abdominal radiographs after surgery.

22 of these patients had radiographs during theearly post-operative period because of obstructivesymptoms, including abdominal distention in 12patients, nausea and vomiting in eight andabdominal pain in eight. The abdominal radio-graphs and medical records were available forreview in the 21 cases who comprised our studygroup.

When abdominal radiographs are obtained inour department for possible intestinal obstruction,the protocol includes both supine and uprightfilms to assess for the presence of free intraperi-toneal air or airfluid levels in the bowel, whereasportable abdominal radiographs are generallyobtained with the patient in a supine positiononly. In our series, the examinations consisted ofsupine and upright abdominal radiographs in 18patients and supine portable abdominal radio-graphs alone in three. Six patients also hadvertical beam left lateral views of the pelvis tofacilitate passage of gas into the rectosigmoid andto differentiate adynamic ileus from distal colonicobstruction more easily [8]. Initial abdominalradiographs were obtained an average of 3 daysafter Caesarean section (range 16 days). 12patients had one set of abdominal radiographsand nine had serial studies, with an average ofthree additional sets of radiographs (range 17).

Received 10 January 2000 and in revised form 3 April2000, accepted 10 April 2000.

Address correspondence to Dr M S Levine.

The British Journal of Radiology, 73 (2000), 951955 E 2000 The British Institute of Radiology

951The British Journal of Radiology, September 2000

The initial abdominal radiographs werereviewed retrospectively by two of the authorsto characterize the bowel gas patterns in these 21patients. A diagnosis of small bowel obstruction,colonic obstruction or adynamic ileus was made,based on the presence and degree of boweldilatation and the distribution of dilated bowel.When the colon was dilated, the distal extent ofcolonic dilatation was also noted. The averageluminal diameter of the dilated small bowel was3.5 cm (range 2.55.5 cm) and the averageluminal diameter of the dilated colon was6.4 cm (range 49 cm). Upright abdominal radio-graphs were evaluated for the presence or absenceof airfluid levels in the dilated loops of bowel.Left lateral projections of the pelvis were alsoevaluated for the presence or absence of gas in therectosigmoid. Finally, radiographs were evaluatedfor the presence or absence of free intraperitonealair, pneumatosis, thumbprinting or a pelvic mass(representing the enlarged post-partum uterus).When more than one set of abdominal radio-graphs had been obtained, all subsequent radio-graphs were reviewed to determine theradiographic course.

As a separate part of the study, the originalradiological reports were reviewed to determinethe impression at the time the abdominal radio-graphs had been obtained. Medical records werealso reviewed to determine the treatment andpatient course.

Results

Radiographic findings

Abdominal radiographs demonstrated findingssuggestive of distal colonic obstruction in 15(71%) of the 21 patients. These patients all hadvarying degrees of colonic dilatation, with orwithout small bowel dilatation, and minimal orno gas in the rectosigmoid (Figures 1a and 2a). Inall cases, airfluid levels were present in thedilated bowel loops on upright radiographs(Figure 1b). In the 15 patients with findingssuggestive of distal clonic obstruction, the de-scending colon was the most distal segment ofdilated bowel in 13 (87%) and the transverse colonin 2 (13%). In all 15 cases, there was increased softtissue density in the pelvis, representing theenlarged post-partum uterus. Of the 15 patients,six also had left lateral projections of the pelvis.In four cases, these additional radiographsshowed minimal or no gas in the rectosigmoid,supporting a diagnosis of distal colonic obstruc-tion (Figure 2b). In the remaining two, theseprojections showed gaseous filling of the recto-sigmoid, indicating a likely ileus.

In 2/21 patients (10%), abdominal radiographsdemonstrated findings suggestive of small bowel

obstruction, with dilated small bowel and apaucity of colonic gas on supine radiographs(Figure 3) and airfluid levels in the dilated smallbowel loops on upright radiographs. Both of thesepatients also had evidence of a pelvic mass. In 3patients (14%), abdominal radiographs showedfindings suggestive of adynamic ileus, with diffusedilatation of small bowel and colon (including therectosigmoid) on supine radiographs and airfluidlevels in the dilated bowel loops on uprightradiographs. These three patients also hadevidence of a pelvic mass. In 1 patient (5%),abdominal radiographs showed a normal bowelgas pattern. There was no evidence of freeintraperitoneal air or of thumbprinting or pneu-matosis of the bowel in any of the 21 cases.

In a separate review of the original radiologicalreports from these 21 patients, the initial impres-sion was a post-operative adynamic ileus in 9(43%), possible colonic obstruction in 8 (38%),possible small bowel obstruction in 3 (14%) and anormal bowel gas pattern in 1 (5%).

Treatment and course

All 21 patients were managed conservatively bystopping oral intake and reducing analgesics.Nasogastric tubes were also placed for decom-pression of the bowel in nine patients, and MillerAbbott tubes in two patients (the two withisolated small bowel dilatation). All 21 patientshad spontaneous resolution of symptoms over anaverage follow-up period of 4 days (range 110days), strongly favouring an adynamic post-operative ileus. Nine patients also had follow-upabdominal radiographs that showed decreasingdistention of small bowel and/or colon over anaverage period of 6 days (range 310 days).Therefore, the follow-up studies also stronglyfavoured a transient post-operative ileus as thecause of these findings.

Discussion

Women may develop a severe post-operativecolonic ileus (also known as colonic pseudo-obstruction) following Caesarean section [17]. Inour study, symptoms severe enough to warrantabdominal radiographs were present in 21patients, which constituted less than 1% of allpatients who underwent Caesarean section duringan 8-year period. 15 (71%) of these 21 patientshad a post-operative ileus that mimicked theradiographic findings of distal colonic obstruction(Figures 1 and 2a). In such cases, the findingswere characterized by dilatation of the colon, withor without small bowel dilatation, and withminimal or no gas in the rectosigmoid.Although the radiographic appearance favoured

B F Kammen, M S Levine, S E Rubesin and I Laufer

952 The British Journal of Radiology, September 2000

(a) (b)

Figure 1. 35-year-old woman with post-operative ileus mimicking distal colonic obstruction, 3 days afterCaesarean section. (a) Supine abdominal radiograph shows dilated colon to the level of the descending colon,with no gas in the rectosigmoid. Also note increased soft tissue density in the pelvis, representing the enlargedpost-partum uterus. (b) Upright abdominal radiograph shows airfluid levels in the dilated colon.

(a) (b)

Figure 2. 31-year-old woman with post-operative ileus mimicking distal colonic obstruction on abdominal radio-graph and vertical beam left lateral projection of pelvis obtained 2 days after Caesarean section. (a) Supineabdominal radiograph shows dilated small bowel and colon, with absence of gas in the rectosigmoid andincreased soft tissue density in the pelvis. (b) Left lateral view of pelvis shows dilated colon (arrows) in the lowerabdomen, with absence of gas in the rectosigmoid, a finding usually indicative of distal colonic obstruction. Theenlarged post-partum presumably compressed the rectosigmoid, preventing it from filling with gas.

Adynamic ileus after Caesarean section

953The British Journal of Radiology, September 2000

a distal colonic obstruction, clinical and/or radio-

graphic follow-up in all cases indicated that these

findings were caused by a transient post-operative

ileus.We considered the possibility that the plain

radiographic findings in these 15 patients could

have resulted from a true mechanical obstruction

by an enlarged post-partum uterus compressing

the rectosigmoid. However, ultrasound studies

have shown that the enlarged post-partum uterus

gradually involutes, returning to its original size

over a period of 68 weeks [9, 10]. If the

radiographic findings resulted from mechanical

obstruction of the rectosigmoid by an enlarged

uterus, these findings would therefore be expected

to resolve gradually as the uterus involuted.

However, the obstructive symptoms in our

patients resolved on conservative management

over an average period of only 4 days, and follow-

up abdominal radiographs showed decreasing

distention of bowel over an average period of

only 6 days. The rapid and dramatic improvement

in these patients therefore indicates that dilatation

of bowel was caused by a transient post-operative

ileus and not by mechanical obstruction by an

enlarged post-partum uterus.

Instead, we believe that the enlarged post-partum uterus prevents gas from entering therectosigmoid in these patients with a post-operative ileus, creating the erroneous impressionof a distal colonic obstruction. When an ady-namic ileus is suspected, left lateral radiographs ofthe pelvis or prone abdominal radiographsfacilitate passage of gas into the rectosigmoid,often enabling differentiation of an adynamicileus from a true mechanical obstruction [8]. Useof these additional projections is based on theassumption that the rectosigmoid will distendwith gas in patients with an adynamic ileus butnot in patients with a distal colonic obstruction.However, the rectosigmoid remained collapsed infour of six patients in whom left lateral radio-graphs of the pelvis were obtained (Figure 2b).This presumably resulted from the enlarged post-partum uterus compressing the rectosigmoid andpreventing it from filling with gas. It is thereforeimportant to recognize that additional projectionsto facilitate passage of gas into the rectosigmoidare unlikely to be helpful in differentiating a post-operative ileus from a distal colonic obstructionfollowing Caesarean section.

On the basis of our findings, we believe thatabdominal radiographs have limited value inpatients with obstructive symptoms followingCaesarean section as the vast majority of patientsare found to have a transient post-operative ileusregardless of the bowel gas pattern. These radio-graphs are mainly helpful for assessing the degreeof dilatation of the bowel and the need fordecompression. For this reason, supine abdominalradiographs are probably adequate in most caseswithout the need for additional upright, decubitusor vertical beam projections. Rarely, however,upright radiographs or even abdominal CT scansmay be required for further investigation ofpatients with clinical signs of post-operativeischaemia or perforation.

Patients who develop an adynamic ileus follow-ing Caesarean section are almost always treatedconservatively, with reduction of oral intake to aminimum, nasogastric decompression anddecreased use of analgesics for pain control.Occasionally, in patients with a severe post-operative ileus, the caecum may become massivelydilated, increasing the risk of caecal perforation[11]. In such cases, a rectal tube or even acaecostomy may be required to decompress thebowel. In our series, however, the ileus resolvedspontaneously in all cases without need forendoscopic or surgical decompression of thebowel.

In conclusion, radiologists should be aware ofthe limitations of abdominal plain radiographsfollowing Caesarean section, so that a post-operative ileus is not mistaken for a distal colonic

Figure 3. 31-year-old woman with post-operative ileusmimicking small bowel obstruction, 5 days afterCaesarean section. Supine abdominal radiographshows dilated small bowel in the left side of theabdomen, with a paucity of colonic gas. Also noteincreased soft tissue density in the pelvis and theMillerAbbott decompression tube with its tip(arrow) in the duodenum.

B F Kammen, M S Levine, S E Rubesin and I Laufer

954 The British Journal of Radiology, September 2000

obstruction and so conservative measures can beundertaken to decompress the bowel until theileus resolves.

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Adynamic ileus after Caesarean section

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