Necrotizing Enterocolitis Flashcards
Necrotizing enterocolitis (NEC) is characterized by which of the following statements?
A. It generally occurs in infants on parenteral nutrition who have not yet had enteral feeding.
B. A single spontaneous perforation occurs, most commonly in the jejunum.
C. It is associated with an immature GI tract, which allows for an increased permeability and bacterial translocation.
D. It almost always requires surgical intervention.
E. It affects premature and term infants with the same frequency.
ANSWER: C
COMMENTS: Although the exact etiology of NEC is unknown, it is likely that it is multifactorial.
It is thought to be related to an unbalanced inflammatory reaction within an immature GI tract that results in the disruption of intestinal integrity.
Translocation of intestinal bacteria follows.
It is directly related to prematurity and low-to-very low birth weights.
Infants at the highest risk for developing NEC are those born before 28 weeks or those having a birth weight less than 1000 g.
Hypoxia is also clearly associated with the disease. Most infants who develop NEC have already had enteral feeding.
NEC may be limited to a single segment of bowel or multiple segments.
The terminal ileum is the most frequent site.
Spontaneous intestinal perforation (SIP) is a similar entity that is characterized by a single perforation in an infant who has never had enteral feeding.
SIP also occurs most commonly in the terminal ileum.
It is thought to be caused by ischemia and has been associated with postnatal indomethacin use.
Radiographs will demonstrate pneumoperitoneum, as in perforated NEC, but will not show portal venous gas or pneumatosis, as is often found in NEC.
Long-term morbidity and mortality are significantly better with SIP than with NEC.
A premature infant with a history of neonatal respiratory distress requiring ventilatory support is being fed oral formula. Abdominal distention develops, and blood-streaked stool is passed. Appropriate management includes which of the following?
A. Anoscopy and addition of Karo syrup for a probable neonatal fissure
B. Immediate barium enema to rule out intussusception
C. Restriction of oral intake to clear liquids to prevent mucosal injury
D. Nasogastric drainage, IV antibiotics, total parenteral nutrition (TPN), and serial abdominal examinations and radiographs
E. Antibiotic-directed treatment of specific pathogens cultured from the stool
ANSWER: D
COMMENTS: This patient has NEC.
Which of the following are indications for surgery in an infant with NEC?
A. Pneumatosis intestinalis
B. Portal venous gas
C. Pneumoperitoneum
D. Bloody stools
E. All of the above
ANSWER:
C
COMMENTS: NEC affects premature infants who have received oral feedings. Clinical manifestations are initial intolerance of formula, abdominal distention, and/or blood-streaked stool and then progression to systemic sepsis, metabolic acidosis, and thrombocytopenia.
Bell’s classification categorizes NEC into three groups:
Stage 1. Suspected NEC. Findings may include gastric residuals, abdominal distension, occult or gross blood in the stool, temperature instability, apnea, and bradycardia. Radiographs are either normal or show bowel dilation consistent with ileus.
Stage 2. Definite NEC with mild-to-moderate systemic illness.
Additional findings include absent bowel sounds, abdominal tenderness, metabolic acidosis, and decreased platelets. Radiographs may show intestinal dilatation, pneumatosis intestinalis, portal venous gas, and ascites.
Stage 3. Advanced NEC. Severe systemic illness with marked distension, signs of peritonitis and sepsis, and hypotension. Radiographs show all of the above and pneumoperitoneum when there is a perforation.
Initial treatment is directed at the prevention of further mucosal injury and septic complications.
Oral feedings are stopped, nasogastric tube decompression is instituted, broad-spectrum antibiotics are administered, and fluid and electrolyte support is provided.
Close monitoring with physical examination, serial radiographs, and biochemical assessment for signs of deterioration are mandatory.
Pneumatosis intestinalis is a pathognomonic radiographic finding of NEC that is caused by the invasion of the bowel wall by gas-forming organisms.
This may be seen in stage 2. Portal venous gas indicates the presence of gas-forming organisms translocated to the portal circulation.
Neither of these radiographic findings is an absolute indication for surgery.
Surgical intervention is necessary when there are progressive clinical deterioration, sepsis, and/or shock, usually due to perforation, persistent intestinal ischemia or necrosis with worsening metabolic acidosis, thrombocytopenia, and hemodynamic instability.
At surgery, the necrotic bowel is resected, and the ends of the retained bowel are brought out as enterostomies.
Bowel preservation is a high priority during surgery to avoid complications associated with the short-bowel syndrome (SBS).
A second-look operation in 24h can be performed if bowel viability is questionable at the first operation.
Which of the following is the most common cause of SBS in the pediatric population?
A. NEC
B. Gastroschisis
C. Malrotation with volvulus
D. Intestinal atresias
E. Long-segment Hirschsprung’s disease
ANSWER: A
COMMENTS: The common causes of SBS in the pediatric population, from most frequent to least, are NEC, intestinal atresias, gastroschisis, volvulus, and, rarely, Hirschsprung’s disease.
A purely functional definition of SBS is a failure to wean from parenteral nutrition after 3 months.
Studies have shown that the presence of at least 35 cm of functional small bowel in neonates is associated with weaning from TPN in 50% of cases.
Patients with SBS require TPN to survive.
Complications of TPN include catheter-associated infections, liver disease, and bacterial overgrowth in the remaining intestine.
TPN-related liver disease occurs in 40%–60% of infants who require long-term TPN.
This may include cholestasis, cholelithiasis, and hepatic fibrosis that may result in biliary cirrhosis, portal hypertension, and liver failure.
The management of SBS is aimed at minimizing these complications and restoring enteral feeding whenever possible.
Medical management includes careful fluid and electrolyte replacement, early enteral therapy to stimulate intestinal adaptation, suppression of early gastric hypersecretion, antibiotics for bacterial overgrowth, and cholestyramine to control bile acid–induced diarrhea.
Surgical lengthening procedures, such as the serial transverse enteroplasty (STEP) procedure, may improve absorption.
Intestinal transplant, often performed with synchronous liver transplant, is indicated when medical management fails.
The management of SBS is often done with a multidisciplinary approach to promote the best adaptation of the remaining intestine.
A long-term survival may be expected in up to 90% of patients; however, they may require extensive medical care.
Discuss NEC.
Necrotizing enterocolitis (NEC) is the most common lethal gastrointestinal (GI) disease in preterm infants worldwide.
It is characterized by severe inflammatory response and intestinal necrosis, and may have a different pathogenesis with than intestinal perforation (FIP).
The symptoms of NEC range from feeding intolerance to lethal courses characterized by perforation, peritonitis, sepsis and shock.
An abdominal X-ray is helpful to identify dilated or fixed bowel loops, pneumatosis, portal venous gas or free air.
Exploratory laparotomy with enterostomy is the most frequently performed surgical treatment.
Alternatives include primary anastomosis or the placement of a primary peritoneal drain.
In case of panintestinal NEC (<25% viable bowel), the options range from aggressive surgical management to comfort measures only.
Long-term sequelae include stric- tures, short-bowel syndrome, growth retardation and neurodevelopmental delay.
Which infants develop NEC?
Children with low birth weight, small for gestational age, low gestational age, assisted ventilation, premature rupture of membranes, black ethnicity, sepsis, and hypotension.
How does the incidence of NEC correlate with birth weight (BW)?
The incidence of NEC in children with LBW (<1500 g) varies worldwide (USA/ Canada 7%, Netherlands 3.9–6.8%, Germany 2.9%).
It accounts for 1–5% of all NICU admissions in the USA and depends on the birth weight.
From stage II onwards (pneumatosis but no surgery; Bell classification, see below) it is reported as follows: 11% with BW 401–750 g, 9% with 751–1000 g, 6% with 1001– 1250 g, and 4% with 1251–1500 g.
What is the typical gestational week (GW) and age of life?
Neonates <28 GW and especially 28–31 GW.
The typical age for NEC is
14–21 days of life.
Which is the associated mortality rate of NEC?
Mortality is as high as 30–50% in those infants requiring surgical management.
Which are the predominant sites of intestinal involvement in NEC?
Isolated small intestinal involvement is noted in 30% of cases.
NEC is limited to the colon in 25% of cases, and the splenic flexure is the most common site of colonic involvement.
In~10%, nearly the entire intestine can be involved (panintestinal NEC).
What are the characteristic pathologic changes of the intestine seen in NEC?
On abdominal X-ray the bowel loops are distended.
The intestines may be encased in a fibrinous exudate.
Subserosal gas collections called pneumatosis intestinalis may be seen.
The extent of the pathologic changes may be classified as focal, multifocal, or pan-intestinal (<25% viable bowel).
What does histologic sectioning of NEC lesions show?
In early stages histopathologic changes in NEC include pneumatosis intestinalis in the submucosa.
In advanced disease transmural necrosis and loss of villus and crypt architecture is seen.
What are the key factors involved in NEC pathogenesis?
Epidemiologic studies demonstrate that NEC incidence is inversely proportional to gestational age at birth.
Therefore, immature intestinal host defenses are thought to play a major role in its pathogenesis.
These key immature defenses include intestinal barrier function, intestinal regulation of microbial colonization, regula- tion of intestinal circulation, and intestinal innate and adaptive immunity.
Which to other phenotypes of neonatal bowel perforation or “pretenders of NEC” are frequently seen?
Focal intestinal perforation (FIP; syn: spontaneous/segmental intestinal perforation): with no demonstrable cause a bowel perforation is typically found in the terminal ileum.
Compared to NEC children are younger, typically <1500 g and most often present in the first week of life.
The definite diagnosis is made at the time of laparotomy.
Prognosis of FIP is better compared to NEC.
Neonatal bowel perforation on the basis of congenital heart defects: A bowel perforation may happen prior or after cardiac surgery most likely due to circulatory disturbances (bowel ischemia).
The typical anatomic location of the perforation is the left colonic flexure.
What are the clinical signs of NEC at presentation?
The clinical findings are often nonspecific: physiologic instability including lethargy, temperature instability, recurrent apnea, bradycardia, hypoglycemia, and shock.
As the disease progresses, abdominal distention/ tenderness, blood per rectum, high gastric residuals after feeding or vomiting may occur.
At a later stage palpable bowel loops, a fixed or mobile mass, or edema and erythema of the abdominal wall or scrotum may be seen.
What alterations in the complete blood count and arterial blood gas analysis are typically associated with NEC?
A frequent combination is neutropenia, thrombocytopenia, and metabolic acidosis.
What are the radiologic findings of NEC on a plain-film?
Early signs: multiple gas-filled loops of intestine with thickened bowel walls.
Pneumatosis intestinalis (presence of gas in the bowel wall with a sensitivity and specificity for NEC of 44% and 100% respectively).
It is caused by hydrogen, a by-product of the metabolism of translocated intramural bacteria.
In which layer does pneumatosis start?
In the submucosa, progressing to the muscularis and subserosal layers.
Portal venous gas—how does it get there? Does it affect prognosis?
It is hypothesized that the genesis of portal venous gas, seen in~33% of cases, may involve accumulation of gas in the bowel wall as a result of bacterial invasion up the venous system from the intestinal wall into the portal veins.
It is associated with worse prognosis (Mortality as high as 54%; 25% panintestinal NEC).
Are contrast studies useful in NEC?
Not in making the diagnosis of NEC, even in case of bowel perforation.
However, contrast enemas or antegrade studies with water soluble contrast media have a value in the evaluation of bowel strictures after NEC prior to closure of the enterostomy.
Who is “Bell”, what is the role of his classification for NEC?
Martin J Bell is a pediatric surgeon from St. Louis, USA who did his fellowship at Cincinnati Children’s Hospital Medical Center. In 1978 Bell defined three stages of NEC [4].
According to this classification the severity of NEC is sub grouped into “suggestive of NEC” (Stage I), “definitive NEC” (Stage II) and “evidence of bowel necrosis and clinical deterioration” (Stage III) based on the patient’s history, gastrointestinal or systemic symptoms and radiologic findings.
What are the components of conservative management of NEC?
Nasogastric decompression, total parenteral nutrition, and broad-spectrum antibiotics.
In case of fungal sepsis empirical antifungal therapy should be considered.
How many children with NEC need surgery?
Approximately 50% of VLBW children.
What are the indications for surgical intervention?
Free air on X-ray (pneumoperitoneum).
Relative indications include a positive paracentesis, palpable abdominal mass, abdominal wall erythema, portal venous gas, fixed intestinal loop, and clinical deterioration despite maximal medical therapy.
How does one determine the extent of bowel to resect?
The goal is to remove only gangrenous bowel and preserve intestinal length.
All other bowel loops with potential for recovery should be left in place and may be reevaluated by multiple-look laparotomies to allow for adequate resuscitation and abdominal decompression.
What do you do in case of multisegmental disease (>50% viable bowel)?
Depending on the case the options include resection with enterostomy, resection with anastomosis, proximal enterostomy, the “clip-and-drop” technique, and the “patch, drain, and wait” technique.
In case of focal NEC, is it safe to perform a primary anastomosis?
Yes, in selected cases, but the classic approach is to create an enterostomy proximal to the resected segment and bring out the distal intestine as a mucous fistula leading to immediate decompression of the bowel in the postoperative period.
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The classic intervention for NEC has been bowel resection with enterostomy and mucus fistula, with reestablishment of bowel continuity at a later time. However, success with resection and primary anastomosis has been reported in a number of publications.
Candidates for primary anastomosis are those with NEC involving a single segment or contiguous segments (i.e., requiring a single anastomosis), healthy remaining bowel, and hemodynamic stability.
A multicenter, randomized controlled trial (STAT trial) is currently in progress to compare outcomes between enterostomy and primary anastomosis.
Sherif
What are your options in case of Pan involvement (NEC totalis,<25% viable bowel)?
Some surgeons take the decision to forego any treatment as the mortality rate is 42 to 100%.
Another option is diverting the intestinal stream by high proximal jejunostomy (without bowel resection) in the hope that the injured bowel heals through distal intestinal decompression.
Does the placement of a primary peritoneal drain (PPD) have better outcome than laparotomy? [5]
PPD versus laparotomy was evaluated in two multicenter RCT.
The US-American NECSTEPS trial (117 children, GA<34weeks, BW<1500g) had a compara- ble outcome after 90 days. The European NET trial (69 children, BW <1000 g) showed similar results.
The mortality rate of the two treatment groups was the same in both trials.
However, in the NET-trial secondary laparotomy was necessary in 74% of cases after 2.5 days.
Other studies show that the highest mortality is seen in children treated by PPD only.
Which intraoperative event during exploratory laparotomy is life-threatening?
Spontaneous intraoperative liver hemorrhage caused by retractors or finger dissection. Therefore liver retraction must be gentle at all times.
Does the location of the stoma and mucous fistula in the same incision cause more wound infection?
No, there is no increase in wound infection rates.
Which are the associated long-term problems of children with NEC?
Strictures, short-bowel syndrome, growth retardation and neurodevelopmental delay.
Which probiotics are given for prevention of NEC, what is the evidence for this treatment? [6]
The most common strains are Lactobacillus and Bifidobacterium.
Multiple RCT and several meta-analyses show that probiotics can lower the risk of late-onset-sepsis and NEC.
However, in children<1500g the evidence for the benefit of routine probiotic supplementation for NEC prevention is less clear.
Also unanswered questions include dosage, type of microorganism and duration of treatment.
Candidates for primary anastomosis are those with NEC include?
- NEC involving a single segment or contiguous segments (i.e., requiring a single anastomosis)
- healthy remaining bowel, and
- hemodynamic stability.
Standard surgical therapy for NEC has been resection of necrotic and gangrenous bowel and stoma formation. However, there have been multiple retrospective case series reporting safety of primary anastomosis in hemodynamically stable patients who have focal NEC.
The advantage of this approach is prevention of a second laparotomy and avoidance of stoma complications, which occur in 50% of patients.
These complications include mechanical problems such as necrosis, retraction, prolapse, stricture, and wound breakdown, as well as functional problems such as fluid loss and sodium loss that prevent adequate growth and weight gain.
A current randomized trial, the STAT trial, is accruing patients and aims to compare enterostomy versus primary anastomosis in NEC patients who meet specific criteria.
Primary anastomosis for SIP in babies weighing less than 1 kg should be considered with extreme caution, as the bowel in these babies is extremely frail and may hold sutures quite poorly.
NEC enterostomies should not be matured but rather tacked to the fascia circumferentially, leaving the bowel end approximately 1 cm above the skin.
Stoma closure is typically performed when the baby reaches a weight of 2 kg, but closure may be hastened if there is significant prolapse or fluid loss limiting enteral feedings.
Sherif
What are the histologic features of NEC you would expect to see on pathologic examination of the specimen?
Resected specimens of intestine involved with NEC show patchy or diffuse transmural necrosis, with extreme parchment-like thinning of the bowel wall, which leads to perforation and peritonitis.
Pneumatosis intestinalis may be seen as well. The histological features of NEC are dominated by coagulative necrosis and hemorrhage of the mucosa in the earlier stage and varying degrees of coagulative necrosis of the muscle layers in later stages.
Vascular thromboses, noted in the most affected areas, are most likely secondary.
The inflammatory reaction in the involved segment, except at the site of perforation, is characteristically minimal or absent.
Focal reparative changes in healing lesions, such as granulation tissue formation, may also be found.
Sherif
What are the five “I”’s characterizing NEC?
Immaturity Insult Ischemia Inflammation Infection
Immature bowel has poor mucosal integrity and an intestinal barrier that may be easily disrupted. Motility is decreased, which leads to bacterial overgrowth and increased exposure to bacterial toxins.
Immunologic defenses are also weaker and often overwhelmed by the inciting insult, which may include underlying respiratory distress syndrome, congenital heart disease, and perinatal infections.
The bowel is not a high-priority organ in premature infants. During periods of stress, the baby shunts blood to the brain and heart at the expense of subdiaphragmatic organs, triggering global intestinal ischemia.
This in turn often results in an exaggerated inflammatory state mediated by nitric oxide and its metabolites. Invasive infection from gut bacteria then follows.
Bell Staging System Classification of NEC?
The Bell staging system has been useful in classifying NEC for purposes of outcome reporting and risk stratification.
Stage I represents suspicious NEC
Stage II represents confirmed NEC
Stage III represents advanced NEC, requiring surgical intervention.
Plain radiographic imaging of the abdomen is the diagnostic imaging modality of choice for diagnosis of Bell stages II and III NEC.
Pneumatosis intestinalis, or air within the bowel wall, is the sine qua non of NEC. A soap bubble or ground glass appearance denotes cystic pneumatosis or air within the bowel wall seen in cross section.
Linear pneumatosis appears when intramural air is seen in longitudinal section, outlining the bowel wall.
Other findings associated with more severe NEC include portal vein gas and fixed loops.
Pneumoperitoneum confirms Bell stage III NEC and is an absolute indication for surgical intervention.
Pneumoperitoneum may be massive and obvious on a supine film, demonstrating a sign known as the sail or football sign. The sail or seam of the football represents the falciform ligament with air on both sides of it.
However, a small amount of free air will only be picked up on a left lateral decubitus film. The decubitus film is preferable to a cross-table lateral in this instance, since air above the liver cannot be confused with intraluminal air.
It must be remembered that all these signs may be absent in patients with NEC at any stage, and the only abnormality may be the presence of an asymmetric bowel gas pattern, distended bowel loops, or a high-grade bowel obstruction.
MD-7 Criteria for NEC?
A set of seven metabolic derangements, referred to as MD-7, has been found to be of diagnostic value in deciding which patients are likely to require surgical intervention.
These include
6 derangements detected on laboratory testing:
- positive blood cultures
- hyponatremia
- acidosis
- leukopenia
- bandemia, and
- thrombocytopenia, and
1 clinical derangement:
- hypotension requiring vasopressor support.
The trajectory of these derangements may be more important than their presence or absence at diagnosis.
Persistence of three or more MD-7 criteria despite medical treatment is strongly associated with necrotic bowel and need for surgical intervention.
Principles for surgery in NEC Totalis?
The surgeon is often faced with a dilemma when multiple segments are involved or a more diffuse type of NEC, referred to as NEC totalis, exists.
In these cases, surgical maneuvers should be dictated by two principles.
First, the hemodynamic status, coagulation status, and temperature stability of the baby should be taken into account. The surgeon may need to go into damage-control mode.
Second, bowel length should be preserved where at all possible.
Options in patients with multiple areas of NEC interrupted by viable bowel include a second look laparotomy, the clip and drop technique (resection of necrotic areas and clipping the proximal and distal margins of each segment), multiple enterostomies, a proximal diverting enterostomy with distal anastomoses (with or without a stent), and proximal diverting enterostomy alone.
The latter option may be preferable in a highly unstable patient.
In hemodynamically stable patients, I prefer a proximal enterostomy and multiple distal anastomoses decompressed proximally through a mucus fistula. These anastomoses can all be “six-stitch” anastomoses, with one stitch at the mesenteric margin, one stitch at the antimesenteric margin, and two stitches on each of the anterior and posterior bowel walls within the margins. I find these anastomoses faster than performing multiple stomas. Since they are all diverted, leakage is not a concern.
The surgeon may also tunnel a Broviac catheter from the mucus fistula past the most distal anastomosis to stent the anastomoses, referred to as a shish-kebab technique.
NEC totalis usually presents with fulminant septic shock and hemodynamic deterioration, despite the absence of free air. Pneumatosis is often diffuse, and portal vein gas may be seen early in the course.
The appearance at laparotomy may be deceiving, as the bowel may still retain its pink color despite diffuse visible pneumatosis. However, the condition is rarely salvageable, and diffuse bowel necrosis usually ensues within 24 hours.
Sherif
Modified Bell Classification for NEC?
Stage I
- Apnea, bradycardia, temperature instability
- Normal gas pattern/mild ileus
- Mild abdominal distention, stool occult blood, gastric residuals
Stage IIA
- Apnea, bradycardia, temperature instability
- Ileus with dilated bowel loops, focal pneumatosis
- Moderate abdominal distention, hematochezia, absent bowel sounds
Stage IIB
- Metabolic acidosis, thrombocytopenia
- Widespread pneumatosis, portal venous gas, ascites
- Abdominal tenderness, edema
Stage IIIA
- Mixed acidosis, coagulopathy, hypotension, oliguria
- Moderate to severely dilated bowel loops, ascites, no free air
- Abdominal wall edema, erythema, insulation
Stage IIIB
- Shock, worsening vital signs and laboratory values
- Pneumoperitoneum
- Bowel perforation
A 13-day-old neonate born at 30 weeks gestation develops poor feeding, abdominal distention, and bloody stools. The mother reports that the patient has just begun bottle feeding. Abdominal radiography shows small amounts of air within the bowel wall.
Which of the following is pertinent to the pathological findings?
Choices:
1. Attenuated myenteric plexus acetylcholine esterase staining
2. Sigmoid volvulus
3. Pneumatosis intestinalis
4. Intussusception
Answer: 3 - Pneumatosis intestinalis
Explanations:
• The signs and symptoms of necrotizing enterocolitis are highly variable, nonspecific, and subtle. Parents often report decreased activity and fatigue. They may also report gastrointestinal symptoms such as decreased appetite, vomiting, diarrhea, and increasing abdominal girth. Patients may also experience blood in the stool.
• As the disease progresses, the patient may experience systemic signs related to respiratory failure and circulatory collapses, such as cyanosis and unresponsiveness.
• Pneumatosis intestinalis is pathognomonic for necrotizing en-terocolitis. The tissue of the intestinal wall in patients with necrotizing enterocolitis shows inflammation and bacterial invasion.
• As the disease progresses, tissue shows ischemia, followed by necrosis, and ultimately perforation, which may be either microperforation or a frank perforation. Microperforation leads to pneumatosis intestinalis or air within the intestine wall. In perforation, the peritoneal cavity becomes contaminated with bacteria and bowel content, leading to peritonitis.
StatPearls
Radiological and laboratory signs that suggest worsening NEC include all of the following except:
A elevated CRP (C-reactive protein)
B portal venous gas on abdominal X-ray
C thrombocytopenia
D metabolic acidosis
E diffuse pneumatosis intestinalis.
A
The presence of diffuse pneumatosis intestinalis and/or portal venous gas on abdominal X-rays is associated with significant NEC.
Persistent thrombocytopenia and metabolic acidosis are part of Bell’s modified criteria and raise the suspicion for bowel perforation.
CRP is usually elevated in inflammatory states; however, it is quite non-specific for the different stages of NEC and its complications.
SPSE 1
A 2-week-old premature baby boy with a birthweight of 900 g, who was being fed formula, suddenly develops episodes of apnoea and bradycardia that require intubation, mild abdominal distension and tenderness, and occult blood in the stool.
His abdominal X-ray shows uniformly distended loops of bowel with gas in the rectum, no pneumatosis intestinalis and no pneumoperitoneum.
Based on this clinical scenario, which of the following statements is most correct?
A This patient has a definite diagnosis of NEC and should be treated with bowel rest, gastric decompression and broad-spectrum antibiotics for at least 7 days.
B This patient has advanced NEC and should be taken immediately to the operating room.
C This patient has suspected NEC. He should be started on broadspectrum antibiotics and abdominal X-rays should be obtained to confirm the diagnosis. Feeds should not be stopped unless there is clear radiological diagnosis of pneumatosis intestinalis.
D This patient has a definite diagnosis of NEC and the length of treatment will depend on the progression of the disease and/or the development of complications.
E This patient has suspected NEC. Initial management includes bowel rest, gastric decompression, broad- spectrum antibiotics, serial X-rays and frequent clinical re-evaluations. Septic ileus could present in a similar fashion.
E
The diagnosis of NEC is based on the presence of general and gastrointestinal signs and symptoms combined with imaging findings. The staging system proposed by Bell has been slightly modified and is still largely utilised worldwide to guide diagnostic and therapeutic decisions.
Based on the criteria in Table 40.1, this case illustrates a patient who clearly has stage 1 (suspected) NEC.
Close follow-up is warranted to determine if the patient will develop definite NEC (stage 2A or worse) with worsening abdominal signs and specific radiological findings such as pneumatosis intestinalis.
Neonatal sepsis can cause an ileus and may be undistinguishable from a diagnosis of suspected NEC.
SPSE 1
Regarding spontaneous intestinal perforation (SIP), which of the following statements is not true?
A It usually happens in the antimesenteric border of the terminal ileum.
B In general, patients are not as critically ill as patients with NEC.
C An association with the use of indomethacin for treatment of persistent ductus arteriosus (PDA) in premature babies has been suggested but never adequately documented.
D It is very easy to differentiate SIP from NEC preoperatively.
E Apart from the perforated site, the rest of the bowel usually looks healthy.
D
Isolated ileal perforation (also called SIP) is often considered a separate entity from NEC.
Usually, patients with SIP are not as ill as patients with NEC, although preoperative distinction between the two is very difficult; an association between SIP and the use of indomethacin for PDA closure has been suggested but never confirmed.
SPSE 1
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Spontaneous intestinal perforation (SIP) has been alluded to in the previous discussion. Debate has raged over whether this disease is a variant of NEC or a completely different pathology.
While it is true that SIP cannot be conclusively diagnosed preoperatively, the disease does seem to affect a different cohort of patients and does possess some unique clinical characteristics.
It is overwhelmingly a disease of extremely low birth weight, premature patients who develop a bowel perforation early in life, before or shortly after feedings are started.
An association with high-dose non-steroidal anti-inflammatory medications used to treat a patent ductus arteriosus has been reported.
The event is usually sudden, and abdominal films can progress from normal to massive free air in hours, without evidence of pneumatosis intestinalis or other NEC-associated radiological findings.
Figure 34.13 shows the films done to evaluate mild abdominal distention in a 4-day-old, ex-26-week-premature neonate and repeat films performed 8 hours later, after the distention increased significantly.
The perforation is typically a discrete, punched-out, single perforation in the distal ileum with no bowel gangrene or necrosis.
Reported treatment modalities have included peritoneal aspiration, peritoneal drainage, surgical closure of the perforation, and bowel resection with primary anastomosis or diversion.
While this population was felt to represent the patient cohort most likely to succeed with peritoneal drainage alone, results have varied widely.
Definitive treatment of SIP with drainage alone has been reported to be successful in 10%–80% in various studies.
Patients who fail drainage often proceed to surgery when they are more unstable.
Some develop a phlegmon and persistent bowel obstruction and require very difficult laparotomies with high risk of bleeding and bowel loss.
In our practice, we only employ peritoneal drainage to temporarily decompress a compartment syndrome, if present. Otherwise, we perform a laparotomy, at which time the perforation is either closed in a transverse manner, if narrow with healthy edges, or resected, if more significant.
When resection is necessary, an enterostomy and mucus fistula or long Hartman (if the perforation is very close to the ileocecal valve) are created. A recent study found a high rate of complications when primary anastomosis is performed in these patients.
Retention sutures using 4-0 nylon and 8-French, latex-free catheter segments may help prevent wound complications in these very fragile patients.
Sherif
Regarding surgical procedures for the management of SBS, which of the following is true?
A A recirculating loop allows for decreased transit time and increased nutrient absorption.
B Before undergoing a lengthening procedure, patients should have intestinal continuity restored if possible.
C In a patient with SBS and a functional obstruction due to a small segment of dilated bowel, resection of the dilated portion is the best surgical option.
D The only benefit of performing a lengthening procedure, such as the Bianchi procedure or STEP, is the increase in intestinal length resulting in decreased transit time and increased nutrient absorption.
E When creating a reversed intestinal segment for a child with SBS, a standard length of 10 cm should be used.
B
The primary goal of surgical intervention is to increase intestinal absorptive and digestive capacity. If possible, patients with diverting stomas should have intestinal continuity restored.
other surgical procedures have been conceived to address the specific anatomical and physiologic anomalies of short bowel patients. These abnormalities include rapid intestinal transit, reduced mucosal surface area, dysfunctional peristalsis, and decreased intestinal length. The various surgical procedures, therefore, may be classified by the defect they were devised to address.
Recirculating intestinal loops are not advised and are addressed here only for thoroughness. Theoretically, creating a loop of intestine that allows luminal contents to recirculate several times before proceeding distally would slow intestinal transit and afford nutrients prolonged exposure to the mucosa for absorption. unfortunately, experimental studies have failed to show benefits. Enteral contents can be radiographically shown to recirculate, but absorption is not improved. Furthermore, morbidity and mortality increase with the complexity of the loop.
Dilated intestinal segments are known to cause functional bowel obstruction. Failure of bowel-wall apposition during contraction results in ineffective peristalsis. The dilated bowel is unable to generate sufficient contraction pressure, resulting in poor forward propulsion of the enteric contents. Stasis of intestinal contents results, leading to bacterial overgrowth, toxin production, and malabsorption. Patients with only a short segment of dilated bowel and sufficient small-bowel length can simply undergo resection of the affected bowel. unfortunately, the bowel of patients with SBS is typically dilated and short, and isolated resection of the dilated segment of bowel is rarely a tenable solution. In this case, patients should undergo either a tapering enteroplasty or a lengthening procedure.
In a tapering enteroplasty, a stapling device is used to longitudinally excise the dilated antimesenteric portion of the intestine. The remaining bowel is, therefore, smaller in calibre and demonstrates improved motility. Antimesenteric plication is an alternative surgical option to reduce bowel diameter. The bowel is folded into the lumen and plicated, which preserves absorptive surface area, while decreasing bowel calibre. unfortunately, over time, the suture lines tend to break down and bowel dilatation recurs. Tapering has much less morbidity than a lengthening procedure and is usually the procedure of choice for patients with a reasonable length of small intestine.
The following proposed algorithm for management of patients with SBS takes into account the presence or absence of intestinal dilatation as the first decision point.
A lengthening procedure not only increases intestinal transit time by increasing intestinal length but also improves peristalsis by decreasing the calibre of the bowel. The procedure of choice depends on the patient’s anatomy and the surgeon’s preference.
The first lengthening procedure was described by Bianchi in 1980, and takes advantage of the anatomical features of the mesenteric blood supply to the bowel. The mesenteric blood vessels bifurcate before contacting the edge of the bowel wall. Each branch supports one half of the bowel circumference. The gut’s vascular configuration, therefore, allows division along its longitudinal axis into two tubes whose circumference is half that of the original bowel. Division and tubularisation of the bowel can be done using either a gastrointestinal anastomosis (GIA) stapling device or a hand-sutured technique. The two newly constructed tubes of bowel are then anastomosed in an isoperistaltic fashion. Thus, the Bianchi procedure effectively doubles the length and halves the circumference of the dilated segment. This technique not only augments bowel length for nutrient absorption, but also improves peristalsis by narrowing intestinal calibre.
The Iowa (Kimura) procedure was developed for bowel lengthening in SBS patients with limited mesentery associated with very short bowel. The procedure is performed in two stages. In the first surgery, the antimesenteric bowel wall is pexed to the undersurface of the abdominal wall to create a systemic-based blood supply for the antimesenteric side of the bowel. A seromyotomy along the bowel wall and mechanical abrasion of the abdominal wall facilitates neovascularisation. Several months later, the bowel may be longitudinally divided into two limbs. The antimesenteric limb now has a systemically derived blood supply, while the other limb continues to utilise the original mesenteric blood supply. These two limbs are then reapproximated to double the intestinal length. This procedure appears to be specifically useful in children, whose remaining bowel is limited to the duodenum. unfortunately, the Iowa procedure is technically very difficult to perform, limiting its applicability.
The most recently developed lengthening procedure is the STEP, or serial transverse enteroplasty, described in 2003. In this procedure, the dilated small bowel is lengthened by serial transverse applications of a GIA stapler, from opposite directions, to create a zigzag channel. Proponents of the STEP cite that the procedure is technically less challenging to perform than the Bianchi procedure, can be performed multiple times in a single patient, and has comparable clinical outcomes with regard to TPN independence and avoidance of intestinal transplantation. Additionally, some studies have found the procedure efficacious for the treatment of bacterial overgrowth in dilated bowel segments of patients who do not have short gut syndrome. Further studies are needed, and a STEP registry has been created to critically evaluate this novel procedure.
A reversed intestinal segment is an operation commonly performed in patients with postvagotomy diarrhoea or dumping syndrome and has been applied to patients with SBS. A ‘physiologic’ valve is created by interposing a segment of bowel in which peristalsis is in the opposite direction. The antiperistaltic bowel provides a break in the peristaltic wave and slows overall gut transit. The length of bowel interposed is significant. using too short a segment may not effectively slow peristalsis, while inserting too long a segment may result in functional bowel obstruction. In adults, 10 cm is the most common length reversed. However, in infants. beneficial effects have been derived from as little as 3 cm of gut being utilised. The segment being reversed should be anastomosed to the most distal region of gut possible to provide maximal intestinal braking and enhancement of mucosal absorption. In patients with extremely short bowel lengths, reversed segments may have limited utility because creating a reversed segment can compromise what little bowel exists.
SPSE 1
What is the value of ultrasound in NEC?
The utility of ultrasound in patients with NEC was first reported in 2005. Since then, several studies have shown a great degree of accuracy in ultrasound’s ability to predict bowel gangrene in the absence of pneumoperitoneum.
Multiple aspects of the bowel and peritoneal cavity are evaluated, including the quality and quantity of peritoneal fluid, bowel wall echogenicity and thickness, intramural air, bowel peristalsis, and bowel perfusion using color Doppler.
Absent perfusion has been shown in some studies to be more sensitive than plain films in identifying gangrenous bowel.
Ultrasound may be repeated every 24 hours if necessary.
Figure 34.9 shows the plain abdominal films and ultrasound findings in a patient with NEC who had severe abdominal tenderness and distention, hemodynamic instability, metabolic derangements on diagnosis, and abdominal film revealing pneumatosis and portal venous gas.
Ultrasound showed some bowel segments with increased perfusion and some with decreased perfusion but none with absent perfusion.
There was no free fluid between the dilated bowel loops, and portal venous gas was confirmed.
The patient was treated medically and made a complete recovery.
The specific skill set necessary to perform an ultrasound assessment of the bowel in a patient with NEC is still not widely available, which has continued to limit the role of this diagnostic modality.
Sherif
What is the anticipated natural progression of NEC?
Bowel stricken by NEC will behave in one of three patterns.
It may recover completely without sequels, it may progress to gangrene or necrosis, or it may recover but develop fixed strictures several weeks after the event.
Strictures occur in approximately 25% of patients with stage II NEC, are almost always in the colon, and are concentrated in the watershed areas, namely the hepatic flexure, the splenic flexure, and the sigmoid colon.
The obstruction is quite distal and often low-grade.
A typical presentation is a baby who develops recurrent abdominal distention once a certain volume of feeding is reached.
Strictures may be focal or long.
Both types are shown in Figure 34.11, which shows one patient with focal strictures at the splenic flexure and sigmoid colon and another patient with a long descending colon stricture. Both patients were treated by left colectomy and primary anastomosis.
These strictures may also be found on routine contrast enema performed prior to enterostomy closure, thereby emphasizing the need for such a study.
Reports of NEC stricture dilatation have been published, but the standard treatment is resection and primary anastomosis.
A very rare delayed complication of medically treated NEC, unknown to many surgeons, is enteroenteric fistula. This may present with obstruction similar to a NEC stricture, but the obstruction is often high-grade and fixed rather than recurrent.
Figure 34.12 shows an enterocolic fistula between the distal ileum and sigmoid colon, presenting approximately 4 weeks after medical treatment of a patient with severe NEC. The fistula was diagnosed on contrast enema. At laparotomy, a hostile abdomen was encountered with a phlegmon involving a segment of distal ileum and the sigmoid colon. The colonic segment was resected and a primary colorectal anastomosis completed. The ileal segment was resected, and the patient was diverted with an ileostomy and mucus fistula. The stoma was closed after a contrast study showed a patent colon without stricture.
Bowel dysmotility can also develop after NEC and limit the ability to advance enteral feedings despite the absence of a mechanical stricture. This often improves with time.
If no improvement is seen, bowel tapering is effective.
If short bowel syndrome coexists, inversion tapering may be used instead of resection tapering to preserve absorptive surface.
NEC is responsible for approximately one-fourth of all cases of short bowel syndrome in children. Ileal involvement and loss of the ileocecal valve are associated with increased risk of intestinal failure.
Recent studies have shown that patients with short bowel due to NEC are more likely to achieve enteral independence earlier than similar patients with intestinal atresia or gastroschisis, probably due to absence of chronic ischemia and dilatation prior to the insult.
Growth retardation and neurodevelopmental delay are other potential long-term risks after NEC.
Sherif
What is the anticipated natural progression of NEC?
Bowel stricken by NEC will behave in one of three patterns.
It may recover completely without sequels, it may progress to gangrene or necrosis, or it may recover but develop fixed strictures several weeks after the event.
Strictures occur in approximately 25% of patients with stage II NEC, are almost always in the colon, and are concentrated in the watershed areas, namely the hepatic flexure, the splenic flexure, and the sigmoid colon.
The obstruction is quite distal and often low-grade.
A typical presentation is a baby who develops recurrent abdominal distention once a certain volume of feeding is reached.
Strictures may be focal or long.
Both types are shown in Figure 34.11, which shows one patient with focal strictures at the splenic flexure and sigmoid colon and another patient with a long descending colon stricture. Both patients were treated by left colectomy and primary anastomosis.
These strictures may also be found on routine contrast enema performed prior to enterostomy closure, thereby emphasizing the need for such a study.
Reports of NEC stricture dilatation have been published, but the standard treatment is resection and primary anastomosis.
A very rare delayed complication of medically treated NEC, unknown to many surgeons, is enteroenteric fistula. This may present with obstruction similar to a NEC stricture, but the obstruction is often high-grade and fixed rather than recurrent.
Figure 34.12 shows an enterocolic fistula between the distal ileum and sigmoid colon, presenting approximately 4 weeks after medical treatment of a patient with severe NEC. The fistula was diagnosed on contrast enema. At laparotomy, a hostile abdomen was encountered with a phlegmon involving a segment of distal ileum and the sigmoid colon. The colonic segment was resected and a primary colorectal anastomosis completed. The ileal segment was resected, and the patient was diverted with an ileostomy and mucus fistula. The stoma was closed after a contrast study showed a patent colon without stricture.
Bowel dysmotility can also develop after NEC and limit the ability to advance enteral feedings despite the absence of a mechanical stricture. This often improves with time.
If no improvement is seen, bowel tapering is effective.
If short bowel syndrome coexists, inversion tapering may be used instead of resection tapering to preserve absorptive surface.
NEC is responsible for approximately one-fourth of all cases of short bowel syndrome in children. Ileal involvement and loss of the ileocecal valve are associated with increased risk of intestinal failure.
Recent studies have shown that patients with short bowel due to NEC are more likely to achieve enteral independence earlier than similar patients with intestinal atresia or gastroschisis, probably due to absence of chronic ischemia and dilatation prior to the insult.
Growth retardation and neurodevelopmental delay are other potential long-term risks after NEC.
Sherif
What is the anticipated natural progression of NEC?
Bowel stricken by NEC will behave in one of three patterns.
It may recover completely without sequels, it may progress to gangrene or necrosis, or it may recover but develop fixed strictures several weeks after the event.
Strictures occur in approximately 25% of patients with stage II NEC, are almost always in the colon, and are concentrated in the watershed areas, namely the hepatic flexure, the splenic flexure, and the sigmoid colon.
The obstruction is quite distal and often low-grade.
A typical presentation is a baby who develops recurrent abdominal distention once a certain volume of feeding is reached.
Strictures may be focal or long.
Both types are shown in Figure 34.11, which shows one patient with focal strictures at the splenic flexure and sigmoid colon and another patient with a long descending colon stricture. Both patients were treated by left colectomy and primary anastomosis.
These strictures may also be found on routine contrast enema performed prior to enterostomy closure, thereby emphasizing the need for such a study.
Reports of NEC stricture dilatation have been published, but the standard treatment is resection and primary anastomosis.
A very rare delayed complication of medically treated NEC, unknown to many surgeons, is enteroenteric fistula. This may present with obstruction similar to a NEC stricture, but the obstruction is often high-grade and fixed rather than recurrent.
Figure 34.12 shows an enterocolic fistula between the distal ileum and sigmoid colon, presenting approximately 4 weeks after medical treatment of a patient with severe NEC. The fistula was diagnosed on contrast enema. At laparotomy, a hostile abdomen was encountered with a phlegmon involving a segment of distal ileum and the sigmoid colon. The colonic segment was resected and a primary colorectal anastomosis completed. The ileal segment was resected, and the patient was diverted with an ileostomy and mucus fistula. The stoma was closed after a contrast study showed a patent colon without stricture.
Bowel dysmotility can also develop after NEC and limit the ability to advance enteral feedings despite the absence of a mechanical stricture. This often improves with time.
If no improvement is seen, bowel tapering is effective.
If short bowel syndrome coexists, inversion tapering may be used instead of resection tapering to preserve absorptive surface.
NEC is responsible for approximately one-fourth of all cases of short bowel syndrome in children. Ileal involvement and loss of the ileocecal valve are associated with increased risk of intestinal failure.
Recent studies have shown that patients with short bowel due to NEC are more likely to achieve enteral independence earlier than similar patients with intestinal atresia or gastroschisis, probably due to absence of chronic ischemia and dilatation prior to the insult.
Growth retardation and neurodevelopmental delay are other potential long-term risks after NEC.
Sherif
