Radiography is the preferred examination for evaluating cases of meconium ileus, meconium peritonitis, meconium ileus–equivalent syndrome, and meconium plug syndrome. [3, 10, 25] (See the images below.)
Contrast enema examination can help in differentiating meconium plug syndrome from meconium ileus or ileal atresia. In these latter conditions, microcolon is seen, and only occasionally does an infant with MI have a picture similar to that seen in an infant with meconium plug syndrome. [26] (See the images below.)
Plain abdominal radiographs frequently reveal a low small-bowel obstruction with numerous air-filled loops of bowel. Although plain imaging findings may suggest the diagnosis, with or without a family history of CF, contrast enema examination of the colon is required to confirm the diagnosis of MI. [7, 21, 27] Water-soluble contrast material is typically used, as are a variety of water-soluble contrast agents. Shin and Jeon reported that ultrasound-guided Gastrografin enema at bedside was effective and safe for very low birth weight infants as first-line treatment to relieve meconium-related ileus. They concluded that with this treatment, unnecessary emergent operation can be avoided in preterm infants, who have high postoperative morbidity and mortality, as can transport of small preterm infants to the fluoroscopy suite. [28] The Cystic Fibrosis Foundation Consensus Conference on GI disorders concluded that no scientific evidence suggests that a hyperosmolar Gastrografin enema is any better than an iso-osmolar or hypo-osmolar enema. However, opinion remains divided on this topic, and Gastrografin when diluted appropriately is used safely by very experienced pediatric radiologists. Other nonionic contrast agents (eg, Hypaque, Omnipaque) are preferred by many radiologists and involve less risk of dehydration or colitis. Because of potential fluid shifts, hypovolemia may occur; therefore, assurance of adequate hydration and electrolyte balance before, during, and after the procedure is essential. This monitoring should prevent significant fluid shifts. If perforation of bowel and leak of contrast or Gastrografin into the peritoneum occurs, more rapid fluid shifts may result. Close monitoring by a neonatologist is recommended. Acetylcysteine (a mucolytic) can be mixed with the enema to aid the passage of very sticky meconium, but the efficacy of this is not known. Because of tenacious meconium and abnormal mucous gland secretion, air-fluid levels often are not apparent. However, images in some infants may reveal air-fluid levels, especially in those with complications such as volvulus and stenosis or atresia. Although absence of air-fluid levels strongly suggests meconium ileus, the presence of air-fluid levels does not exclude it. In some cases of MI, distention of the obstructed small bowel can be enormous and findings can be easily misinterpreted as distal colonic distention. In other cases, a so-called soap-bubble effect of gas mixed with meconium may be seen. Although this soap-bubble effect is not pathognomonic of the condition, it is commonly seen with MI. However, it can also be seen with ileal atresia, colonic atresia, Hirschsprung disease, and meconium plug syndrome. A contrast enema study typically demonstrates microcolon, which reflects underused bowel. A microcolon can be due to other etiologies besides CF such as ileal atresia or another complete intrauterine obstruction of the distal small bowel. However, when contrast agent refluxes into the small bowel, meconium pellets distending the distal ileum are usually identified and the diagnosis of MI is confirmed. Meconium peritonitis may be incidentally detected on abdominal radiographs. The extruded meconium may or may not become calcified, and when no calcification is present, the radiograph may only suggest fluid in the abdomen. Contrast enema examination can help in differentiating meconium plug syndrome from MI or ileal atresia. In some cases, fluid and meconium can pass into the chest, presumably through congenital communications, resulting in meconium thorax. When calcification is seen, the diagnosis can usually be confirmed. This calcification can be amorphous and irregular or curvilinear, with the latter suggesting cystic loculation or coating of the peritoneum. The term "cystic" or "pseudocystic" meconium peritonitis has been applied to this finding. It is uncommon to encounter an older child with residual calcifications. Only occasionally does an infant with MI have a picture similar to that seen in an infant with meconium plug syndrome. Plain abdominal images show a mottled appearance (which may simulate meconium) in dilated loops of small bowel. Other plain imaging findings include a bubbly, granular appearance, predominantly on the right side of the abdomen, with dilated small bowel and fluid levels due to small-bowel obstruction. Water-soluble contrast enemas are often helpful in excluding other possible causes of symptoms and can be used to treat patients with this condition. If the diagnosis can be made radiologically, conservative medical treatment should be pursued vigorously, and surgery should be undertaken only if it is unavoidable. [22] Meconium plug and small left-colon syndromes are diagnosed radiologically, and contrast enema examination is required. Plain images are nonspecific and usually show findings of a low small-bowel obstruction. Erect abdominal radiographs, albeit seldom necessary in the newborn, show a paucity of air-fluid levels, and, in most cases, no gas is seen in the colon. Water-soluble contrast enemas can be curative with the passage of meconium. If air is introduced into the rectum from below (eg, on rectal examination), rectal gas may be visualized. In this setting, meconium in the rectum can erroneously suggest a small presacral mass. However, if air entirely surrounds the meconium mass, it will outline the contour of the mass, suggesting the correct diagnosis. If peristalsis forces gas from the small bowel into the colon, and if the gas mixes with meconium, a granular or bubbly appearance mimicking the findings of pneumatosis cystoides intestinalis and necrotizing enterocolitis (NEC) results. If a bubbly pattern is seen within the first 12 hours of life, meconium plug syndrome should be considered, but if it is visible after 12 to 18 hours, NEC is more likely. NEC typically occurs in preterm infants. Contrast enema examination shows a characteristic appearance of the colon, with contrast material outlining the solid column of inspissated meconium and the wall of the colon for a double-contrast effect. After meconium is passed, the portion of the colon from which it was evacuated may appear narrowed, and a transition zone mimicking that seen in Hirschsprung disease may be noted. In any of these cases, meconium proximal to the apparent transition zone may take the form of a solid, cylindrical mass extending to the cecum, or lumps of solid meconium may be scattered throughout the colon. For patients with intermediate findings, individual assessment is most important. The small, contracted portion of the descending colon in these infants has led to the term "neonatal small left-colon syndrome." Differentiating Hirschsprung disease from meconium plug or small left-colon syndrome can be a problem, and one must completely exclude Hirschsprung disease before either of these diagnoses is confirmed. [8] Initial clinical and radiologic findings may be similar, but infants with Hirschsprung disease invariably return with either constipation or diarrhea. Once treated, those with meconium plug or small left-colon syndrome remain healthy. Plain images in infants with Hirschsprung disease are more likely to show numerous air-fluid levels on the erect view. During an enema, abnormal contractions with bowel wall irregularity may be seen in the narrowed, aganglionic bowel of Hirschsprung disease, but the bowel wall typically has a smooth contour in the meconium plug setting.
Meconium ileus is among the most common causes of intestinal obstruction in the newborn, accounting for 9-33% of neonatal intestinal obstructions. It is the earliest clinical manifestation of cystic fibrosis (CF) and occurs in either a simple or a complicated form in approximately 16-20% of patients who have CF, though it also occurs in patients who do not have CF. In the simple form, thickened meconium begins to form in utero. It obstructs the midileum, causing proximal dilatation, bowel wall thickening, and congestion. Complicated meconium ileus may cause volvulus, atresia, necrosis, perforation, meconium peritonitis, and pseudocyst formation. Clinically, CF is characterized by the following triad:
A possible meconium ileus diagnosis should raise the suspicion of CF in the fetus. Antenatal diagnosis of meconium ileus can be confirmed in 2 groups. In the low-risk group, the diagnosis is suspected when routine prenatal ultrasonography reveals the sonographic appearances of meconium ileus. The high-risk group consists of all pregnancies subsequent to the birth of a child with CF. Parents of a child with CF are obligate carriers of a CF mutation. Go to Cystic Fibrosis and Sinonasal Manifestations of Cystic Fibrosis for complete information on these topics. Fetuses with CF have abnormal development of the pancreas and intestinal tract. Expression of the cystic fibrosis transmembrane conductance regulator gene (CFTR) can be detected in the pancreatic ductules at 18 weeks’ gestation. In patients with CF, abnormal pancreatic secretions obstruct the duct system, leading to autodigestion of the acinar cells, fatty replacement, and ultimately, fibrosis. Beginning in utero, this progressive process occurs variably over time. Approximately two thirds of infants later diagnosed with CF by neonatal screening have pancreatic insufficiency at birth. Approximately 10% of patients with CF remain pancreatic sufficient and tend to have a milder course. Surgical exploration is indicated for patients with progressive distention, signs of peritonitis, or clinical deterioration. Surgery is always indicated for complicated meconium ileus. Complicated meconium ileus requires resection more often than simple meconium ileus and always requires temporary stomas. The following complications necessitate surgical management: Complicated meconium ileus may cause volvulus, atresia, necrosis, perforation, meconium peritonitis, and pseudocyst formation. Infants with meconium ileus are at risk for cholestasis, particularly if they have received or are receiving total parenteral nutrition (TPN). Monitor alkaline phosphatase, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin levels weekly. An observational study of infants with CF and meconium ileus identified the following risk factors for poor outcomes: high blood immunoreactive trypsinogen levels, prenatally diagnosed intestinal obstruction, a severe post-surgical clinical picture, and early liver disease. [1] Gastroesophageal reflux (GER) is more prevalent in patients with CF, and it may exacerbate the respiratory status of the patient with CF. Pathologic reflux (ie, endoscopic and histologic esophagitis) is present in more than 50% of patients with CF. Most CF patients have an abnormal quantity of reflux as defined by pH probe, and it has been reported with prominent respiratory symptoms. Early diagnosis and treatment of this condition are of prime importance if the complications of pathologic reflux are to be curtailed and respiratory function maximized. The particular mechanism of GER in CF is unclear, but a number of factors may contribute to the increased susceptibility of this patient group to the development of pathologic GER. First, most reflux episodes in CF occur during transient lower esophageal sphincter (LES) relaxations. These transient relaxations are increased during distension of the gastric fundus, a feature that can predispose these patients to reflux especially when receiving large supplemental bolus feeds. This cycle of events may be further exacerbated in the event of poor gastric emptying. Gastric emptying of liquids was initially thought to be delayed in patients with CF. Second, the head-down posture adopted during chest physiotherapy places gastric liquid content in an optimum position at the LES for reflux in the event of a transient period of relaxation. Associated coughing and forced expiration, which both increase the abdominothoracic pressure gradient, also facilitates reflux action. Last, medications such as theophylline and beta-adrenergic drugs, used in the treatment of respiratory disease in patients with CF, are known to decrease the resting tone in the LES and could conceivably facilitate reflux activity. Biliary tract disease is another important consideration. Gallbladder disease is prevalent in the CF population, with abnormal oral cholecystograms in 46% and cholelithiasis in 12%. Abnormalities described in patients with CF include a microgallbladder containing thick colorless “white bile” with occlusion of the cystic duct, gallstones, biliary dyskinesia, and sclerosing cholangitis. Bile acid metabolism is disturbed in patients with pancreatic insufficiency who are not receiving adequate pancreatic enzyme supplementation. Bile acids are likely bound to malabsorbed fat and, as a result, are lost in feces, which in turn depletes the bile acid pool and supersaturates cholesterol in the gallbladder. This condition promotes stone formation. Many patients with CF and gallbladder sludge or stones are asymptomatic, but approximately 4% have the classic symptomatology of cholecystitis. A laparoscopic cholecystectomy is the treatment of choice in such cases because postoperative pain and therefore pulmonary compromise are less with this technique than with the classic open technique. The role of cholecystectomy in patients with asymptomatic gallstones remains unclear. Distal intestinal obstruction syndrome (DIOS), also referred to as meconium ileus equivalent, is a recurrent postneonatal partial or complete intestinal obstruction unique to patients with CF. Most cases occur in adolescents and adults, but all age groups can be affected, with an overall incidence of approximately 15%. [2] The exact etiology of DIOS is unknown, but these patients are more likely to have a history of steatorrhea from pancreatic exocrine insufficiency despite adequate enzyme therapy. One study also showed that, of 27 patients with DIOS, 17 (63%) had a history of meconium ileus as an infant. A number of aspects peculiar to the gastrointestinal (GI) function of CF patients may help, in part, to explain this syndrome. These include abnormal intestinal mucins, abnormal intraluminal water and electrolyte content, and inherently slow intestinal motility. The latter may be because neurotensin, a GI hormone that delays motility, is secreted from the distal ileum when unabsorbed fat reaches that location. Additional precipitating factors may include relative dehydration, especially in a postoperative period, inadequate enzyme supplementation, and changes in diet. The cardinal features of DIOS are cramping abdominal pain, often localized to the right lower quadrant (RLQ), a palpable mass in the RLQ, and decreased frequency of defecation. Different degrees of obstruction are present, from partial, which is most common, to complete with vomiting, distension, and absolute constipation. Colicky pain may be provoked by meals, which may then result in anorexia as a method to avoid further pain. Physical examination in uncomplicated DIOS usually reveals a tender mass in the RLQ with no evidence of peritonitis. No fecal impaction or dehydrated stool is noted on rectal examination, and the stool is heme negative. The nonspecific nature of DIOS, with no pathognomonic radiologic features, means that an accurate diagnosis of abdominal pain in the patient with CF is not easy. Plain supine and erect abdominal radiography is still, however, the most helpful initial investigation when the diagnosis is suspected. This shows bubbly granular material in the right iliac fossa and variable degrees of small-bowel obstruction, ie, air-fluid levels with proximal small-bowel dilatation. Plain radiography supports, but does not prove, the diagnosis. Inspissated material in the right iliac fossa can also be demonstrated with a water-soluble contrast enema. In doing so, intussusception can be excluded, and the investigation itself may prove therapeutic in some cases of DIOS. Particular difficulty is faced in the event of partial small-bowel obstruction caused by adhesions from previous abdominal surgery or appendiceal disease, which occurs in 1.5-2% of patients with CF (a lower incidence than the 8.6% noted in the general population). Abdominal pain is a common symptom in patients with CF, and, because these patients are often already being treated with antibiotics and steroids, the classic clinical signs and symptoms of appendicitis may be masked and the critical diagnosis missed. This results in a high incidence of perforation and substantial morbidity in this patient group. Despite the blunting of clinical signs, evidence of pyrexia and a leukocytosis may still be present. Depending on the appendix location, a contrast enema may show deformity of the cecum with an associated mass effect and not the typical inspissated material features of DIOS. Abdominal ultrasonography or, if necessary, computed tomography (CT) scanning shows free fluid or an abscess collection in the region of the cecum. In such cases, treatment should then proceed with appendectomy. If the diagnosis is still in doubt, the surgeon could opt to start with a laparoscopic investigation and then proceed appropriately in light of the findings. In the absence of partial small-bowel obstruction due to adhesions, appendiceal disease, or complete obstruction, DIOS is suitable for a trial of medical management. After adequate rehydration, a balanced polyethylene glycol–electrolyte solution may be administered orally or via nasogastric tube. The dosage is 20-40 mL/kg/h with a maximum of 1200 mL/h. Prokinetic agents, such as metoclopramide, can be used to limit the amount of nausea and bloating. Successful treatment is judged by the passage of stool, resolution of symptoms, and the disappearance of a previously palpable right iliac fossa mass. Sequential plain abdominal radiography helps to document the resolution of DIOS, but, if symptoms persist, the differential diagnoses already outlined must be reconsidered. The use of enemas at the diagnostic stage is outlined. Contrast enemas should also be used for patients with emesis due to DIOS after placement of a nasogastric tube for gastric suction. As long as the patient remains clinically stable, the contrast enemas may be repeated at intervals of several hours over several days. However, careful monitoring of the patient must be initiated before, during, and after the procedure because large fluid and electrolyte shifts can be induced by the contrast material. When complete obstruction or evidence of peritonitis is present, surgical intervention is necessary and all oral or rectal therapies are contraindicated. A nasogastric tube should be passed to help with decompression, and adequate resuscitative measures should be initiated. At laparotomy, the bowel wall feels thickened and filled with tenacious material. It can be decompressed and irrigated with diatrizoate meglumine, usually via a small catheter placed through the appendix stump. An irrigating tube may also be left in situ for postoperative bowel irrigation. The overall risk of cancer in patients with CF is similar to that of the general population; however, risk of gastrointestinal neoplasms is increased. These include tumors of the esophagus, stomach, small intestine, large intestine, liver or biliary tract, and pancreas. The differential localization and expression of CFTR may play a role in the neoplastic disease process. Furthermore, increased cellular turnover in response to the persistent irritation of GER, gallstones, or steatorrhea in digestive tract organs may also offer an explanation to these findings. Fibrosing colonopathy is a newly described entity in children with CF. A longitudinal study showed that, of the children with CF who developed fibrosing colonopathy, 89% (8) of patients underwent surgery, and 63% (5) of them received a subtotal colectomy. Findings at laparotomy in children with CF who presented with presumed DIOS that did not respond to medical therapy included colonic strictures with histopathological changes of postischemic ulceration repair, with mucosal and submucosal fibrosis, destruction of the muscularis mucosa, and eosinophilia. In some patients, a change from conventional enteric-coated pancreatic enzymes to high-strength products 12-15 months before presentation has been described. The diagnosis of fibrosing colonopathy should be considered in patients with CF who have been exposed to high doses of pancreatic enzymes and present with symptoms of abdominal pain, distension, chylous ascites, change in bowel habit, or failure to thrive. Continued diarrhea may also be a prominent feature, which unfortunately may prompt the family to increase supplemental enzymes further. On occasion, the diarrhea may be bloody. A barium enema may reveal mucosal irregularity, loss of haustral markings with a foreshortened colon with varying degrees of stricture formation. In some cases, the whole colon has been involved. Colonoscopy may show an erythematous mucosa and areas of narrowing, from which taking multiple forceps-pinch biopsies is advisable. Initial management should reduce enzyme dosage to the recommended levels of 500-2500 lipase units/kg per meal. This should be accompanied with adequate nutritional supplementation, which may be enteral elemental feeding or even TPN for a time. Those patients who show signs of unrelenting failure to thrive, obstruction, uncontrollable diarrhea, or chylous ascites then need surgical intervention. When elective surgery is planned for patients with intractable symptoms, gentle bowel preparation can be administered preoperatively. The aim of surgical intervention is to resect the affected bowel and make a primary anastomosis. Unfortunately, this is not possible in the event of pancolonic or rectal involvement, and, as a result, the patient requires an ostomy. This is often the safest option; patients and parents must be fully aware and prepared for it preoperatively. Whether this condition completely resolves with a reduction in enzyme dosage and surgical resection is unclear, so the operated group also requires regular follow-up for any signs of deterioration. Rectal prolapse occurs in approximately 20-23% of patients with CF. The initial prolapse occurs most commonly in patients aged 1-3 years and can be recurrent in nature. It may also be the sole presenting feature of a new patient with CF in about 4-8% of all cases. Factors that directly predispose this group to prolapse include constipation, diarrhea with increased frequency and volume of movement, malabsorption, and colonic distention. Indirect contributors relate to increased intra-abdominal pressure caused by coughing or pulmonary hyperinflation. Initial management involves manually reducing the prolapse. Medical management to maximize fat absorption then aids the overall control. Reassure parents that the number of prolapse episodes is likely to reduce with age. However, further intervention is warranted in a small group when they have persistent pain or incontinence with each episode of prolapse. The acute prolapse is easily reduced if action is taken promptly before edema formation. Parents can be taught to grasp the herniated bowel with the fingertips of a gloved hand and apply circumferential pressure with an inward push. Sustained pressure may be required to achieve full reduction. If prolapse immediately recurs, then the buttocks can be strapped together with adhesive tape for 7-14 days. Recurrent prolapse can be treated by means of a rectal submucosal injection, performed with general anesthesia after the rectum has been emptied with a suppository. With the patient in the lithotomy position, the needle is inserted through the skin just outside the mucocutaneous junction and guided into position by a finger placed in the rectum. As the needle is slowly withdrawn, 2-3 mL of 5% phenol in almond oil or hypertonic sodium chloride solution (30%) is injected in a linear track into 4 different quadrants. A single treatment controls approximately 90% of cases. Linear electrocauterization in the 4 quadrants has also been described to produce a perirectal inflammation. This technique requires a longer hospital stay and may be complicated by rectal bleeding and/or rectal stenosis. When all conservative options are exhausted, a surgical approach may then be considered. However, many different operations have been described to control rectal prolapse. Through a transabdominal approach, the rectum can be fixed to the hollow of the sacrum by a prosthetic or fascia lata graft sutured to the bowel and the presacral fascia, thus creating a new pelvic floor. Other operations include rectal suspension and levator ani muscle repair through a posterior sagittal approach. The diversity of options highlights the unsatisfactory results often achieved in these difficult cases. |
Which condition is appropriate to assess for when caring for an infant who has meconium ileus
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