Appendicitis revisited: New insights into an age-old problem

By Barbara M. Garcia Peña, MD, George A. Taylor, MD, and DennisP. Lund, MD

A thorough but speedy evaluation is essential when examininga child with possible appendicitis. In ambiguous cases, CT--especially whenperformed with rectal contrast--is an excellent adjudicator.

Sir Zachary Cope once said, "Acute appendicitis can mimic virtuallyany intra-abdominal process, and therefore to know acute appendicitis isto know well the diagnosis of acute abdominal pain."¹ Althoughit isn't hard to recognize a classic case, the clinical picture is oftenmuddled, and the consequences of a missed diagnosis can be disastrous. Thisreview will clarify the symptoms to look for in the history, the signs toassess during the physical, and the degree of confidence to place in variouslab tests and radiologic studies.

A common emergency

Acute appendicitis is the most common cause for emergency abdominal surgeryin childhood. Some 60,000 to 80,000 cases are diagnosed each year in theUnited States.²

The average age of children with appendicitis is 10 years; girls andboys are equally affected prior to puberty. The lifetime risk of appendicitisis approximately 7%. For unknown reasons, appendicitis develops more frequentlyduring the summer season and in children living in the upper Midwest.³

Despite strong emphasis on early surgical intervention, the morbidityand mortality of acute appendicitis in children remain high. Measurabledeath rates range from 0.1% for nonperforated appendicitis to 5% for perforatedappendicitis.^4,5 Death is usually due to complications associatedwith delayed diagnosis. Approximately one third of inflamed appendixes inchildren are perforated at initial presentation. Since abdominal pain isquite common in children, the small window of time prior to rupture--about36 hours after the abdominal pain begins--can pass quickly and easily. Within48 hours, the appendix will have perforated in 80% of children.²As a result, early recognition of acute appendicitis by pediatricians iscritical.

About the appendix

The appendix is a vestigial, small diverticulum, which arises from thececum. Its function remains unknown. Its anatomic position varies, rangingfrom the pelvis to any position on the right side of the abdomen. A retrocecalposition often makes the diagnosis confusing. In addition, the locationof the appendix in children with intestinal malrotation is highly variable,making the diagnosis even more difficult.

The pathophysiologic cause of acute appendicitis is the obstruction ofthe lumen of the appendix, most often by fecal matter, such as a fecalith.Swollen reactive lymphoid tissue, frequently occurring after a viral illness,can also cause an obstruction. Although it's rare, parasites, particularlyEnterobius vermicularis or pinworm, and carcinoid tumors may obstruct theappendiceal lumen and lead to acute appendicitis.

Multiplication of bacteria in the obstructed appendix leads to swellingand invasive infection of the appendiceal wall. The swelling activates stretchreceptors in the blood vessels of the appendix, which are perceived by thechild in the periumbilical region, the T10 dermatome. As the infection worsens,the appendix exudes inflammatory fluid into the adjacent parietal peritoneum,where it causes localized right lower quadrant pain. If the inflammatoryprocess continues, the appendix will usually perforate.

Direct erosion by the fecalith through the infected appendiceal wallcan cause perforation, while the infected vascular thrombosis can lead togangrene. If the inflammatory, infected fluid leaks throughout the abdomen,the outcome will be generalized peritonitis. However, if the infection isconfined, localized tenderness and a walled-off abscess may develop. Nonetheless,if the infection is not controlled, generalized septicemia and shock willbe the unfortunate final outcome.²

History starts with sequence of symptoms

The most reliable information gained from taking a history from a childwith suspected appendicitis is the sequence of symptoms. Periumbilical painis the earliest symptom of acute appendicitis. In a classic case, a childawakens from sleep with vague periumbilical pain that reaches peak intensityin four hours, and then subsides as it migrates to the right lower quadrant.If the appendix lies in a retrocecal position, however, peritoneal irritationdoes not occur and the pain remains in the periumbilical location. Aftera few hours, the child may vomit. With appendicitis, vomiting usually followsthe periumbilical pain; in children with gastroenteritis, it usually precedesabdominal pain. The absence of vomiting does not exclude a diagnosis ofappendicitis, and many patients progress to perforation without vomiting.Although anorexia is a common and reliable symptom of appendicitis in adults,up to half the children with appendicitis may say they are hungry.

Once inflammatory fluid seeps into the peritoneum, there is direct contactwith the rectosigmoid area of the colon. Subsequently, the colon becomesirritable and begins to produce a low-volume or mucousy type of stool. Frequent,high-volume, watery diarrhea is more commonly associated with gastroenteritis.The temperature may be slightly elevated in acute appendicitis, but usuallyno more than one or two degrees in children without perforation. Fever isoften a late finding in children with appendicitis and is not a reliablesign.²

Exam focuses on right quadrant tenderness

The most reliable finding in a physical examination in acute appendicitisis localized tenderness in the right lower quadrant, two thirds of the waybetween the umbilicus and the anterior iliac spine. This area is known asMcBurney point (Figure 1).⁵ A wise examiner immediately asksa patient to indicate the spot of greatest tenderness so that this areacan be examined last. The examiner can also use a stethoscope for palpationin challenging examinations to alleviate anxiety while appearing to be listening.A frightened child usually tolerates an abdominal examination best if sittingon a parent's lap.

As irritation of the anterior peritoneum progresses, other physical signsdevelop. Figure 2 shows how they are elicited.⁵

Voluntary guarding is a voluntary contraction of the abdominal muscles,held stiff because the child is anxious or because further examination ispainful. Often present in children with appendicitis, guarding can alsobe faked by the child or induced by an examiner who has cold or rough hands.It can be partially or fully overcome by reassurance to the child.

Involuntary guarding. This powerful physical sign, also known as rigidity,is an involuntary reflex spasm of the abdominal muscles in response to peritonealinflammation. It usually develops after voluntary guarding and cannot beovercome by reassurance.

Rebound tenderness. This is elicited by an examiner pressing down onthe tender area slowly, holding for a few seconds, then rapidly removingher hand. The child will suddenly wince if there is peritoneal irritation.Rebound tenderness can also be assessed in other ways. A patient who complainsof pain with every bump in the road on the ride to the hospital is experiencingrebound tenderness, as is a child who has pain when she coughs or who winceswhen she jumps off the examination table. In addition, many clinicians usethe heel-drop-jarring test to evaluate rebound in children. In this test,a child stands, lifts himself on his toes for 15 seconds, and then comesdown with his entire weight on his heels. This maneuver causes pain if thereis peritoneal irritation.

Rovsing sign. The examiner presses deeply in the left lower quadrantand then suddenly releases the pressure. If the child feels pain in theright lower quadrant with pressure or referred rebound tenderness in theright lower quadrant during release of pressure, Rovsing sign has been elicited.^2,4

The signs just described are common in peritonitis of the anterior abdominalwall, seen with an appendix that is anteriorly placed. However, retroperitonealirritation may not generate these physical findings, but may produce othersigns instead.⁵ These include:

Psoas sign. To check for irritation of the psoas muscle, have a patientlie on her back and ask her to lift her thigh against your hand, which isplaced just above her knee. Another way to elicit this sign is to placethe patient in the left lateral decubitus position and have her extend herright leg at the hip. Increased pain with either of these maneuvers indicatesirritation of the psoas muscle by an inflamed retrocecal appendix.

Obturator sign. This sign is often present when there is retroperitonealirritation. Have the patient lie on her back with the right knee and hipflexed. Then internally rotate the child's right leg. The sign is positiveif the maneuver causes increased abdominal pain on the right side due tothe irritation of the obturator muscle by an inflamed appendix.

Rectal examination. A rectal examination is essential for any child withsuspected appendicitis. Although findings may be normal, high pelvic sidewalltenderness on the right side or a pelvic mass or fullness may indicate aninflamed or perforated appendix. The examiner can prevent excessive discomfortin the child during the rectal examination by asking her to push down asif having a bowel movement and then to relax as a finger is inserted inthe rectum.^2,4,5

Laboratory evaluation helps but isn't conclusive

Patients with acute appendicitis frequently present with an elevatedwhite blood cell (WBC) count and a shift to the left in the differential.Studies of patients with abdominal pain and other signs and symptoms ofappendicitis have shown the sensitivity of a WBC count above 11,000/mL andpercentage of neutrophils >75% to be 76% and 78% respectively, and thespecificity to be 74% and 60% respectively in the diagnosis of appendicitis.⁶Although the WBC count is the most common laboratory test ordered for patientswith suspected appendicitis, its value is limited. The WBC count is influencedby many things and is not dependable in diagnosing appendicitis. A normalWBC count does not exclude appendicitis, since it is not uncommon to seea WBC count below 5,000/mL in a child who appears well with a nonperforatedappendicitis. In addition, most children who have been vomiting have anelevated WBC count. However, the WBC count usually does not exceed 20,000in a child with nonperforated appendicitis.² Be that as it may,an elevated WBC count accompanied by classic clinical findings helps makethe diagnosis of appendicitis more certain.⁷

Urinalysis, also commonly performed in children with suspected appendicitis,is used to exclude pathology of the urinary tract. One must remember thatan inflamed appendix lying near the bladder may produce signs of infectionon urinalysis, however. So a child with abdominal pain treated with antibioticsfor a urinary tract infection should be closely followed to be sure thatsymptoms resolve.²

A relatively new laboratory test that aids in the diagnosis of appendicitisis the measurement of serum C-reactive protein (CRP). CRP is an acute phasereactant that rises within 12 hours of onset of infection. Studies haveshown that CRP is elevated in 85% of patients who have had symptoms formore than 12 hours and do have appendicitis.^8,9 However, thetest has low specificity, since any infectious process will cause an elevatedCRP.^2,9

Radiological evaluation

If the clinical presentation and laboratory evaluation of the child withright lower quadrant pain are classic for appendicitis, no confirmatoryradiographic studies are required. When the diagnosis is in doubt, however,the conventional abdominal radiograph (KUB) is frequently the first imagingstudy obtained. The most common finding in KUB in children with appendicitisis right-sided curvature of the spine. In addition, a dilated cecum withan air-fluid level may be seen. A calcified appendicolith is seen in 10%to 15% of children with appendicitis.¹⁰ However, even the presenceof a fecalith in KUB is not pathognomic for appendicitis as many normalappendixes have been removed with fecaliths present. When the appendix hasperforated, there may be decreased bowel gas in the right lower quadrant,an increase in the thickness of the lateral abdominal wall because of freeperitoneal fluid and soft-tissue edema, and a soft-tissue mass in the rightlower quadrant.² Hence, the KUB is often not helpful in diagnosingappendicitis and the findings, even when abnormal, are usually nonspecific.

The use of ultrasonography (US) in the diagnosis of appendicitis in childrenhas increased steadily over the past decade. US can be performed quicklyand is cost-effective, well tolerated, and readily available. Reported sensitivityrates are between 75% and 89%, and specificity rates are between 86% and100%.^11­15 In addition, US has beenshown to change patient management for the better and to minimize negativelaparotomies.¹⁶ When the US shows a thickened or noncompressibleappendix measuring 6 mm or more in diameter, an appendicolith, or a complexmass (Figure 3), its positive predictive value for appendicitis is quitehigh. US is also helpful in evaluating adolescent females with right lowerquadrant pain since the test frequently identifies ovarian cysts or torsionthat may mimic appendicitis.

On the "con" side, US is highly operator dependent, is technicallydifficult to perform on obese patients, and rarely visualizes the normalor the inflamed retrocecal appendix. In addition, a recently perforatedappendix may be impossible to visualize with US because the appendix isno longer distended with fluid. In fact, an air-containing abscess may resemblea bowel or obscure other important findings. Clearly, then, a negative USdoes not exclude appendicitis, and the physician's confidence in a negativeUS result cannot be high. Management of children with suspected appendicitisis generally not based on negative US examinations.

Conventional computed tomography (CT) employing oral and intravenouscontrast has traditionally been used in patients for whom the clinical diagnosisof appendicitis is uncertain. Advances in CT imaging with high-resolutiontechniques have yielded a sensitivity as high as 100% and specificity ashigh as 98%^12,17­19 for the diagnosisof acute appendicitis. The highest accuracy (98%) has been reported witha new, focused appendiceal CT technique using contrast administered onlythrough the rectum.^17­19 For this test,water-soluble contrast material is introduced into the colon via a smallrubber rectal catheter. Thin contiguous cuts of the right lower quadrantare then obtained. CT with rectal contrast (CTRC) better defines the anatomyof the appendix and can identify the normal appendix 94% to 100% of thetime (Figure 4). If the appendix is enlarged (>6 mm in maximum diameter)or inflammatory changes around the appendix are visualized, the diagnosisof appendicitis can be made (Figures 5 and 6). If appendicitis is not thediagnosis, CT can usually establish an alternative diagnosis.

CTRC is easily and quickly performed, requiring less than 15 minutesfrom start to finish. Patient discomfort is minimal, and the radiation exposureis one third that of a standard abdominopelvic CT examination. In addition,studies have shown that the use of CT in children with equivocal clinicalpresentations could markedly reduce complications and acute-care costs associatedwith clinically suspected appendicitis.²⁰

CTRC should be reserved for those children in whom the diagnosis of appendicitisis uncertain after full clinical evaluation. Many physicians believe thatUS should be the primary diagnostic test for children with suspected appendicitisdue to its high positive-predictive value, noninvasiveness and lack of radiation.If the US is negative or inconclusive, and the clinical suspicion remainshigh, CTRC should then be performed. However, CTRC without preliminary USmay be justified for obese children and those with unusual clinical presentationsthat prompt concern.

CTRC costs approximately $200 more than US. Considering that many childrenwith a negative or indeterminate US are subsequently hospitalized for observation,performing CTRC after US is clearly cost-effective since children withoutappendicitis could be safely discharged and return home while those withappendicitis could move expediently to the operating room.

Perforated appendicitis

Over 70% of children younger than 2 years of age will have perforatedappendixes by the time of initial presentation. The child with a perforatedappendix immediately experiences a period of resolving symptoms becausepressure within the lumen of the appendix has been relieved. Soon after,the child will lie still, often drawing up the right leg or both legs. Thevomiting pattern may change from vomiting once or twice or not at all tomore frequent and more bilious vomiting from a paralytic ileus. Fever above101° F is not uncommon. The signs of peritoneal irritation may be localizedor diffuse, and there may be a palpable mass.²

Many children with a perforated appendicitis have what the parents call"diarrhea," which often leads to the wrong diagnosis of gastroenteritis.However, the loose stool accompanying a perforated appendicitis consistsof low-volume, irritative fluid from inflammation of the colon and decreasedperistalsis. Conversely, gastroenteritis produces high-volume diarrhea inassociation with increased peristalsis.²

If the child with a perforated appendicitis is not diagnosed within abouta week, a large walled-off appendiceal abscess is very likely to be present.Once the abscess begins to leak into the abdominal cavity, the child showssigns of toxicity with mottling of the skin, oliguria, evidence of sepsis,and a falling platelet count.²

Differential diagnosis

Appendicitis is frequently mistaken for many common abdominal conditions(Table 1). Since some of them are communicable, it is important to ask aboutother sick family members, any illnesses in the community, and whether thechild has taken any antibiotics recently. The following are the more commonpediatric illnesses that mimic appendicitis:

Gastroenteritis. Undoubtedly, gastroenteritis is the most common conditioncausing abdominal pain in children presenting to the pediatrician for evaluation.Signs that help distinguish appendicitis from gastroenteritis are shownin Table 2. Of the bacterial pathogens, Yersinia, Salmonella, Shigella,and Campylobacter may cause right lower quadrant pain. In fact, the painmay shift from the periumbilical region to the right lower quadrant, asit often does in appendicitis. A high WBC count with a shift to the leftis common and the child may appear quite toxic with a high fever and severecramps. The diagnosis is made from culture of the organism from the stool.²

Constipation. This condition is a common cause of pain in children, particularlyolder children. The pain in the right lower quadrant may be crampy, intermittent,or constant, but it does not progress. Constipation in children is mostoften seen during the heat of the summer months or the dry winter monthswhen heat is used in homes. During both seasons, a contributing factor ischronic mild dehydration.² Often, it is not possible to elicita history of constipation from a child with abdominal pain. If the plainabdominal radiograph shows a feces-filled colon, however, a small enemacan be given. If the symptoms improve after a large bowel movement, thediagnosis of constipation can be made more confidently.²

Mesenteric adenitis. There is a great deal of uncertainty concerningmesenteric adenitis as a legitimate diagnosis. Standard pediatric textbooksdo not even recognize this condition. Nonetheless, mesenteric adenitis hasbeen defined as an inflammation of the lymph nodes clustered in the mesenteryof the terminal ileum. Often, a viral infection with pharyngitis precedesthe abdominal pain by four or five days. Before advanced imaging techniqueswere available, the diagnosis of mesenteric adenitis could not be made priorto surgery. With advances in US and the advent of CTRC, however, the diagnosiscan be made more readily.^21,22

Urinary tract infection. Infection of the urinary tract may produce focalright lower quadrant pain, but fever and leukocytosis in the child are oftenincreased out of proportion to the abdominal pain. If pyuria is present,the child may be treated with antibiotics. If the diagnosis is in doubt,however, appendicitis still must be considered and the patient closely followed.²

Inflammatory bowel disease. Terminal ileitis usually has a more protractedcourse than acute appendicitis. Often patients suffer for months from crampyabdominal pain and diarrhea. Occasionally, the initial presentation of Crohndisease or ulcerative colitis will be similar to acute appendicitis. Thediagnosis can usually be made with CT (Figure 7) or at laparotomy.

Pelvic inflammatory disease (PID). Inflammation of the female upper genitaltract has become more common in recent years. The lower abdominal pain isoften preceded by menses and differs from the pain of appendicitis in thatit usually begins in both lower quadrants rather than in the periumbilicalarea. Cervical motion tenderness is the hallmark of PID and there may bebilateral adnexal tenderness as well. To help exclude the diagnosis of PID,a full pelvic examination on all sexually active females is imperative.In addition, the sedimentation rate is usually over 15mm/hr in PID whilein appendicitis the sedimentation rate is almost always normal. Imagingfindings in patients with PID are typically nonspecific.²

Ovarian cyst. Pathology of the ovary, particularly rupture of an ovariancyst, can closely mimic appendicitis. The pain often starts abruptly, occursmid-cycle, and is located in the right lower quadrant with associated tenderness.There may also be vomiting, particularly with torsion of the ovary. A USoften demonstrates free fluid, other larger or hemorrhagic cysts in theovary (Figure 8), or a recently ruptured follicular cyst.²

Pneumonia. Right lower lobe pneumonia may cause referred right lowerquadrant pain through the tenth and eleventh thoracic nerves. If the childhas a productive cough with respiratory distress, a radiograph of the chestshould be obtained. One should not be fooled, however, by a child whoseright lower lobe infiltrate and fever do not resolve after antibiotic therapy.The underlying pathology may be the localized rupture of a high retrocecalappendix with a collection of fluid under the right diaphragm.²

Challenge and reward

Appendicitis continues to be a diagnostic challenge to the practicingpediatrician. To diagnose it successfully requires a thorough history andphysical examination. Also essential is an understanding of the underlyingframework of the pathophysiology and evolution of the disease. In diagnosticdilemmas, laboratory and radiological examinations may prove helpful. Successfuldiagnosis of appendicitis can yield the ultimate reward in medicine: thecure of a child with a potentially life-threatening disease.

Dr. PEÑA is Fellow in the Department of Medicine, Division ofEmergency Medicine, Harvard Medical School, Boston.

Dr. TAYLOR is Professor of Radiology, Department of Radiology, at thesame institution.

Dr. LUND is Assistant Professor of Surgery, Department of Surgery, atthe same institution.

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Barbara Pena,George Taylor,Dennis Lund. Appendicitis revisited: New insights into an age-old problem. Contemporary Pediatrics 1999;9:122.