The Acute Abdomen

Eduardo J. Schnitzler

Tomas Iölster

Ricardo D. Russo

KEY POINTS

The most frequent cause of acute abdomen in previously healthy children is acute appendicitis.

Acute appendicitis in infants and small children may have an unclear initial presentation. It is sometimes associated with diarrhea, and the diagnosis is often delayed until after it progresses to generalized peritonitis.

The most frequent cause of intestinal obstruction is acquired adhesions, the management of which may only require decompression and intestinal rest.

Timely diagnosis of intussusception is critical to facilitate a quick resolution and avoid progression to intestinal ischemia and obstruction.

Midgut volvulus associated with malrotation is a severe condition with rapid development of ischemia; if suspected, it requires an urgent surgical consultation for a decision regarding surgical intervention.

During the care of newborns, especially premature infants, necrotizing enterocolitis (NEC) remains prevalent and carries a high risk of morbidity and mortality in severe cases. The prevention, early diagnosis, and appropriate combined clinical-surgical management of NEC are essential to improve survival and reduce long-term morbidity.

Severe acute pancreatitis is less frequent in the pediatric population; however, it can be devastating when accompanied by local and systemic intense inflammatory responses.

The most frequent pediatric abdominal complications seen in the pediatric intensive care unit include gastrointestinal hemorrhage, postoperative ileus, acalculous cholecystitis, pseudomembranous colitis, toxic megacolon, and abdominal compartment syndrome.

Recognizing the etiology of abdominal pain or of episodes that simulate the acute abdomen in systemic illnesses, such as diabetic ketoacidosis, acute porphyria, sickle cell crisis, Henoch-Schönlein purpura, or Kawasaki disease, is essential for adequate management.

INTRODUCTION

The term acute abdomen is a clinical syndrome characterized by rapid onset of signs and symptoms indicating an intra-abdominal pathology that requires prompt decision making and often emergent surgical intervention. Presenting signs might include abdominal pain, signs of inflammation, or other symptoms. A diverse spectrum of diseases may produce similar signs and symptoms that culminate in abdominal pain. Accurate and timely clinical assessment is essential to diagnose the underlying pathology and begin appropriate medical or surgical treatment (1).

EVALUATION OF THE EVIDENCE

Due to the paucity of medical evidence, most of the decisions related to the management of children with acute abdomen in the pediatric intensive care unit (PICU) are based on consensus or expert opinion. Conversely, most of the published controlled clinical trials or prospective series are from the adult population; unfortunately etiology, complications, and clinical scenarios differ considerably from those found in children.

To help evaluate the available literature, we use the following modified quality of evidence grading (2) in this chapter:

1. Grade A—decisions based on systematic reviews, metaanalysis, or at least one randomized, controlled trial applicable to the adult critical patient (A−) or the pediatric critical patient (A+).
2. Grade B—evidence based on at least one cohort study or case-control studies applicable to the adult critical patient (B−) or the pediatric critical patient (B+). Only recommendations based on this type of evidence (A or B) are emphasized.
3. Grade C—evidence based on case series, consensus, or expert opinion.

CLINICAL ASSESSMENT

Causes of acute abdomen are listed in Table 101.1 and are divided into three diagnostic groups:

primary abdominal pathology (originating from the gastrointestinal tract);
abdominal pathology as a consequence of critical illness (secondary); and
abdominal manifestations in some systemic diseases that may present as acute abdomen.

Four basic processes may provoke signs and symptoms of acute abdomen: infection or inflammation, obstruction, perforation, and ischemia. A fifth process, gastrointestinal hemorrhage, may be associated with acute abdomen, and is described in more detail in Chapter 99. Most patients with primary abdominal pathology do not require admission to the PICU, provided that diagnosis and treatment (usually surgical) are instituted promptly. However, if the child’s abdominal pathology progresses to ischemia and perforation, the severity
of this presentation with the risk of multiorgan dysfunction necessitates perioperative care in the PICU.

TABLE 101.1 CAUSES OF ACUTE ABDOMEN

Primary abdominal pathology
	Mechanical obstruction
		Intussusception, peritoneal adhesion, others
	Acute intestinal ischemia
		Malrotation, volvulus, others
	Infection/inflammation
		Peritonitis, intra-abdominal abscess, fistula Enteritis, neutropenic enterocolitis Acute pancreatitis Acute cholecystitis^a
	Hollow viscera perforation Abdominal trauma Diseases linked to the reproductive organs
Abdominal pathology of the critical patient
	Gastrointestinal hemorrhage Ileus Pseudomembranous colitis Toxic megacolon Abdominal compartment syndrome
Abdominal manifestations of systemic diseases
	Diabetic ketoacidosis Acute intermittent porphyria Henoch-Schönlein purpura Kawasaki disease Sickle cell crisis
^aCholecystitis can also present as an abdominal pathology of the critical patients.

The critically ill patient may present with complications that compromise the function of the gastrointestinal tract. Intestinal ileus, acute cholecystitis, toxic megacolon, abdominal compartment syndrome, intra-abdominal collections, and tertiary peritonitis are some of the complications of critical illness that may contribute to the patient’s morbidity and mortality. These complications may progress to multiorgan failure and subsequent death.

Finally, diverse systemic diseases may cause conditions that generate or simulate an acute surgical abdomen. The history and clinical examination may be suggestive of a systemic disease that presents as an acute abdomen caused by direct or indirect lesions of the gastrointestinal tract. (Please refer to Table 101.1.)

The etiology and the rapidity of disease progression dictate the clinical presentation and the condition of the patient. A volvulus-associated bowel ischemia usually progresses rapidly to a life-threatening situation, unless it is promptly recognized and treated. An acute appendicitis, if unrecognized or treated inappropriately, may lead to a critical condition. Any one of the conditions assigned to the diagnostic groups in Table 101.1 may necessitate admission to the PICU for monitoring and management of multiorgan failure. Timely recognition may be challenging as patients often manifest with multiple organ dysfunction and deterioration of consciousness. Clinical presentations may overlap among the three groups; hence a strict classification or categorization is not intended. Rather, the goal of this chapter is to distinguish scenarios and to outline an approach that allows diagnosis and management in a timely fashion.

INITIAL MANAGEMENT OF THE CHILD WITH AN ACUTE ABDOMEN

Primary Evaluation and Stabilization

One of the most important initial determinations to be made is whether the patient requires an urgent laparotomy or laparoscopy for diagnosis and treatment. The initial approach, as in any other emergency, includes a quick assessment of the severity of the condition and the potential complications (Fig. 101.1). If the child is clinically unstable or if an intra-abdominal catastrophe is a possibility, establishing an adequate airway, ensuring gas exchange, and maintaining circulation must be prioritized. Intra-abdominal catastrophe may be suspected based on clinical examination. The presence of severe abdominal distension, board-like rigidity, abdominal ecchymoses, or discoloration may be signs of a severe abdominal condition. Monitoring of pulse oximetry, heart rate, electrocardiogram, and noninvasive blood pressure is essential to guide therapy. Two large-bore peripheral venous catheters for vascular access should be established as quickly as possible, and blood and urine samples should be obtained for complete blood count, coagulation profile, chemistries, blood typing and cross matching, blood cultures, and urine studies. Fluid boluses should be administered rapidly until appropriate perfusion has been established, and empiric broad-spectrum intravenous antibiotic treatment should be initiated whenever an infectious etiology is suspected. Early surgical review and imaging studies, such as abdominal radiography and/or ultrasound, may guide therapeutic decisions.

If perforation, peritonitis, or ischemic bowel compromise is suspected, immediate surgical intervention is necessary. If the diagnosis is not clear, further options include an abdominal computerized tomography (CT) scan, an observation period with serial abdominal examination, or an urgent diagnostic surgery (exploratory laparotomy). When bowel obstruction is suspected, initial management will depend on the probable cause and the presence of clinical signs compatible with ischemia. In these patients, nil per os and placement of a nasogastric (NG) tube for stomach decompression are necessary.

History

As soon as the child is stable and intra-abdominal catastrophe is ruled out, a detailed history of the presenting signs and symptoms and sequence of events should be obtained. The presentation and sequence of such symptoms as fever, vomiting, diarrhea, constipation, urinary symptoms, and pelvic symptoms in female teenagers are important for the diagnosis. When possible, localization and radiation of the pain should be determined. History should include previous medical pathologies, previous surgery, chronic drug therapy, recent trauma, and possibility of accidental ingestion of harmful substances in young children. This process is usually undertaken simultaneously as primary evaluation and stabilization of airway and cardiorespiratory status is ongoing.

Physical Examination

Following initial resuscitation, the clinical examination of the abdomen should be thorough and systematic. Inspection may reveal significant findings, such as distension, masses, hernias, surgical scars, or other alterations in the skin. The presence of petechiae, purpura, or rash may be suggestive of a

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