SMALL LEFT COLON SYNDROME

BACKGROUND

• Intestinal obstruction is one of the most frequent reasons for obtaining surgical consultation in newborns• Distal intestinal obstruction of the newborn may be anatomic (eg,

imperforate anus, colonic atresia, colonic stenosis) or functional. Most cases of functional colonic obstruction are caused by Hirschsprung disease• a subset of term or near-term babies experience colonic obstruction with a

characteristic caliber reduction in the sigmoid and descending colon, unrelated to meconium inspissation or aganglionosis.

• In 1974, Davis coined the term small left colon syndrome in his initial description of 20 infants with colonic obstruction not caused by a meconium plug or Hirschsprung disease.[5] In all patients, a contrast enema revealed a narrowed descending and sigmoid colon, with a caliber transition at the splenic flexure; of these, 17 patients experienced immediate and complete resolution of obstruction without operation. Although Davis observed that 8 of the 20 infants were born to mothers with diabetes mellitus, he hypothesized that the apparent dysmotility syndrome was neurogenically determined.

• In 1975, Philippart et al reported 8 patients with a similar clinical and radiographic presentation, all born to mothers treated for gestational diabetes mellitus with either insulin or oral hypoglycemic agents.[6] In 4 of 8 cases, resolution of obstruction after contrast enema was uncomplicated. One patient presented with a cecal perforation requiring emergency operation, one patient underwent operation for suspected Hirschsprung disease (which was subsequently disproved by biopsy), and 2 patients required a delayed operation (one for persistent obstruction and the other for sudden distension and cecal perforation occurring after institution of oral feedings).

• Neonatal small left colon syndrome is an uncommon cause of neonatal intestinal obstruction characterized by an abrupt intestinal caliber transition at or near the splenic flexure and associated, in approximately half of cases, with a maternal history of gestational diabetes mellitus.

EPIDEMIOLOGY

• The frequency with which neonatal small left colon syndrome occurs is difficult to estimate because the entire subject literature contains only case reports and a few case series

ETIOLOGY

• Although the precise cause of this form of neonatal intestinal obstruction, which has a typical radiologic picture but is distinctly unusual, is unknown, numerous theories have been proposed, including neural, humoral, and drug-induced etiologic mechanisms.

• In 1974, Davis et al reported the association of neonatal small left colon syndrome with abnormalities of intestinal neurohistology.[5] Their initial report described increased numbers of immature small ganglion cells in the myenteric plexus (in both the narrowed and dilated portions of the colon) in 4 of 20 patients with neonatal small left colon syndrome. They compared the histology from patients with small left colon syndrome with that of control subjects, including infants of diabetic mothers without colon changes, premature infants, and term infants. They concluded that the hypercellularity observed in the specimens from patients with neonatal small left colon syndrome most closely resembled the histology observed in the colons of premature infants. Despite this conclusion, they did not provide gestational age data on the patients; therefore, at least some of them assumably were premature

• In a 1975 report, Philippart et al focused on humoral and autonomic nervous system changes, which occur in response to neonatal hypoglycemia in developing a mechanistic explanation.[6]

• Glucagon release and sympathoadrenal stimulation are typical in vivo responses to hypoglycemia, and both result in blood glucose stabilization through hepatic gluconeogenesis and glycogenolysis. Along with several effects on the GI tract, glucagon release is known to decrease motility in the jejunum and left colon. Hypoglycemia also stimulates sympathetic and parasympathetic arms of the autonomic nervous system. Maximal vagal (parasympathetic) stimulation results in increased motility in its area of distribution, which ends at the splenic flexure, whereas sympathetic stimulation results in diminished motility. Therefore, a composite effect of glucagon release with sympathetic and parasympathetic nervous system stimulation would hypothetically be an overall diminution in intestinal motility, with a functional block in the colon beyond the splenic flexure.

• In 1991, Schofield and Yunis reported an association in 7 patients with clinical and radiographic neonatal small left colon syndrome and suction rectal biopsy histology demonstrating intestinal neuronal dysplasia (IND).[7] In all 7 cases, the biopsies, which were stained with hematoxylin and eosin (H&E) and acetylcholinesterase (AChE), demonstrated an increase in the number of AChE-stained fibers in the mucosa and increased submucosal ganglia or large ganglia. These changes are also observed with prematurity, and because most of the infants with neonatal small left colon syndrome in this report were indeed premature, gestational age seems to have had a confounding effect on the biopsy results.

DIAGNOSTIC IMAGING

• The diagnosis of neonatal small left colon syndrome on contrast enema examination is based on the following fluoroscopic findings: • (1) proximal dilation of colon (and, to a lesser extent, small bowel) with

abundant intraluminal meconium; • (2) an abrupt cone-shaped caliber transition at or just distal to the splenic

flexure; and • (3) a constricted but smooth contoured, and often foreshortened,

descending and sigmoid colon devoid of meconium with a slightly larger caliber rectum

Contrast enema of an infant who presented with abdominal distension, bilious nasogastric aspirates, and failure to pass meconium at 24 hours of life demonstrates a normal caliber rectum, a small caliber sigmoid and descending colon with an abrupt caliber transition at the splenic flexure. These findings are characteristic of neonatal small left colon syndrome (NSLCS

MEDICAL THERAPY

• IV fluid• NGT decompression• IV antibiotics• Contrast enema, not only diagnostic but also can be

therapeutic

SURGICAL THERAPY

• Surgery is reserved for infants with intestinal perforation or for those in whom obstruction is refractory or recurrent, despite appropriate conservative measures. Surgery in infants with intestinal perforation includes the following• Following appropriate fluid, antibiotic, and, if necessary, blood product

resuscitation, the infant is taken to the operating room and explored, usually through a transverse upper abdominal incision. • Once the point of perforation has been identified, consideration should be

given to determining the diagnosis because, in most cases, Hirschsprung disease still has not been excluded at this time.

• Assuming that the infant's condition is stable and a pathologist with the appropriate expertise is available, seromuscular biopsy samples from the distal colon, in what obviously would appear to be aganglionic bowel, should be obtained for frozen section examination. If a distal biopsy is aganglionic, biopsy samples should be obtained near the transition zone and proximally to localize the transition zone, and a stoma should be created in ganglionic bowel. If the transition zone is at the splenic flexure, leaving the distal aganglionic bowel in place as a long Hartman pouch is reasonable; however, if the transition zone is in the small bowel, a decompressive mucous fistula should be created. In cases of long segment disease, the aganglionic colon should be left undisturbed so as to retain all subsequent reconstructive options.

COMPLICATIONS

• Refractory or recurrent obstruction• After the diagnosis of neonatal small left colon syndrome (NSLCS) has been

adequately established, the need for surgical intervention seems unlikely. Historically, most operations have been performed because of a mistaken diagnosis of Hirschsprung disease, although Philippart et al reported 2 patients who required delayed operations and did not have aganglionosis; one patient developed recurrent obstruction after initial successful enema decompression and required transition zone colostomy, and the other developed an obstruction with cecal perforation 6 days after institution of oral feedings

OUTCOME AND PROGNOSIS

• Most infants completely respond to contrast enema decompression and are able to progress quite rapidly to full enteral feedings. Numerous patients who have undergone follow-up examinations of their colon have demonstrated normalization of caliber within a few weeks. In a 1975 report, Philippart et al warned of the small number of patients who experience delayed complication, either recurrent or persistent obstruction or delayed perforation, mandating close surveillance during the first week or 2 of life