Acute Appendicitis

(1)     Introduction

 The appendix is a true diverticulum of the cecum, its base originating at the confluence of the teania coli. The appendix is relatively large at birth and progressively decreases in size until age 5 years. Its position with regard to the cecum can be variable and this explains its many potential presentations when inflammation occurs. Variable presentations are also common in the extremes of age.

  • Acute appendicitis is the most common surgical disease of the abdomen. The goal of therapy is rapid diagnosis and treatment before rupture.  Perforation occurs in up to 20 percent of patients and is reported to occur in 50 percent of patients at the extremes of life (less than 3 years and greater than 50 years of age). Between 6 and 20 percent of the population develop acute appendicitis during their lifetime.

(2)     Pathophysiology

 By definition, the pathologic finding in acute appendicitis is mucosal disruption with invasive infection and inflammation.  The invasive organisms, consistent with normal stool flora, include E. Coli, Klebsiella, and Enterobacter. The inciting event is thought to be luminal obstruction, most commonly from a fecalith (40 percent of perforated appendicitis) or lymphoid hyperplasia (most commonly in children).  However, not all luminal obstructions cause acute appendicitis and certainly not all acute appendicitis is caused by obstruction.  Following obstruction the appendix continues to secrete into a closed lumen causing increased luminal pressures with eventual venous congestion and infarction along the watershed region.  Eventual perforation is preceded by mucosal ulceration and transmural necrosis. Abscess formation or peritonitis may ensue.

 (3)     Presentation

(a)  Differences in sex and age at presentation will alter the initial clinical scenario. Children less than 5 years of age and adults over the age of 50 will typically present later in the disease process and frequently with vague signs and symptoms.

(b)  With acute appendicitis, vague epigastric and periumbilical pain presents early and is described as a dull ache.  This pain is regulated by autonomic visceral pain fibers. Nearly 95 percent of patients will experience a pain similar to this described.  Anorexia is present in 90 percent of patient’s at this stage.  In fact, if a person is hungry upon history taking, the diagnosis of acute appendicitis must be questioned.  Approximately 4 to 6 hours after initial onset of illness the inflammation extends, activating the somatic pain fibers and localizing the pain to the region of the appendix.  This is most commonly in the right lower quadrant at McBurney's point;  however, the variability of anatomic locations of the appendix (retrocecal, etc.) may cause the pain to be localized in almost any region. A good history is the most helpful tool in making a diagnosis.

(c)  Acute appendicitis is known as the great imitator and can cause right upper quadrant pain, perineal and rectal fullness and pain, and a collection of other presentations.  Acute appendicitis should be in the differential diagnosis for anyone presenting with acute abdominal pain.

(d)  Once the pain localizes, it is common to find the patient very still with voluntary guarding. Cutaneous hyperesthesia is present over the point of maximal tenderness and pain.  A low-grade temperature is now very common (38 °C) and now a low-grade leukocytosis is also commonly present (WBC of 12,000 to 16,000).  A WBC greater than 18,000 is not generally seen at this point of the process and should suggest another possible diagnosis.  Certainly after perforation a high WBC is not uncommon.  Progression will lead to perforation and either abscess formation with the associated signs and symptoms.

(e)  Other signs on examination include right lower quadrant pain with palpation in the left lower quadrant (Rovsing's sign), obturator internus (obturator sign), and psoas sensitivity (psoas sign).  These are indicative of peritoneal inflammation.  Increased pain upon coughing (Dunphy's sign) is less consistent. Patients with symptoms present for over 48 hours are unlikely to have acute appendicitis, as this process will typically take less than 24 hours to manifest.

(4)     Differential Diagnosis

(a)  As stated earlier, the female patient not uncommonly presents with signs and symptoms consistent with acute appendicitis, however up to 40 percent of young women explored for appendicitis had a negative surgical exploration of the appendix.  Salpingitis, ruptured ovarian follicle, and ectopic pregnancy must be considered as the diagnosis with the appropriate work-up initiated.  Surgical exploration is, however, warranted if any question remains regarding possible acute appendicitis.

(b)  Mesenteric lymphadenitis and associated viral gastroenteritis are the most common diagnoses found when acute appendicitis is ruled out.  The symptom complex and progression as well as a careful history and physical examination will provide diagnostic clues. Very rarely will a patient with acute appendicitis first present with diarrhea and high fevers.  This is more suggestive of a viral complex with gastroenteritis as the primary diagnosis.

(c)  Other considerations in the differential diagnosis of abdominal pain resembling acute appendicitis include:

  • Gastroenteritis (viral or bacterial)

  • Acute regional ileitis ( crohn’s disease )

  • Ureteral colic

  • Salpingitis

  • Ruptured ovarian follicle

  • Ovarian torsion

  • Ectopic pregnancy

  • Diverticulitis

  • Perforated ulcer

  • Cholecystitis

  • Perforated neoplasm

  • Urinary tract infection

(5)     Treatment

(a)   Appendectomy is the correct treatment for most patients with acute appendicitis.  Patients presenting late in their disease progression with either a periumbilical phlegmon or abscess may initially respond to non-operative antibiotic therapy.  Surgery should be performed only by qualified surgeons. The initial treatment of appendicitis can be intravenous antibiotics, bed rest, NPO, and semiurgent or urgent medical evacuation.

(b)   Ultimately those patients treated non-operatively should undergo interval appendectomy 6 to 8 weeks after their episode of appendicitis. This form of treatment may be the only course available for the active duty member stationed at a remote site where surgical consultation is not readily available.  In this instance the patient should receive intravenous fluid therapy, be kept NPO, and receive broad-spectrum antibiotics covering the common gastrointestinal flora, specifically gram (-) rods and anaerobes.  A good combination is Unasyn 3.0 grams IV every 6 hours and Flagyl 500mg IV every 6 hours.  A broad-spectrum cephalosporin such as cefotan is also acceptable. Whenever possible, surgical consultation should always the first choice.  The typical recovery from a non-complicated appendectomy is10-14 days.  Active duty members whose job requires physical activity should be withheld from activity for approximately 4 weeks.

Submitted by CAPT William Liston, MC, USN, Head, Department of Surgery, Naval Medical Center Portsmouth, Portsmouth, Virginia (1999).


Preface  ·  Administrative Section  ·  Clinical Section

The General Medical Officer Manual , NAVMEDPUB 5134, January 1, 2000
Bureau of Medicine and Surgery, Department of the Navy, 2300 E Street NW, Washington, D.C., 20372-5300

This web version of The General Medical Officer Manual, NAVMEDPUB 5134 is provided by The Brookside Associates Medical Education Division.  It contains original contents from the official US Navy version, but has been reformatted for web access and includes advertising and links that were not present in the original version. This web version has not been approved by the Department of the Navy or the Department of Defense. The presence of any advertising on these pages does not constitute an endorsement of that product or service by either the Department of Defense or the Brookside Associates. The Brookside Associates is a private organization, not affiliated with the United States Department of Defense. All material in this version is unclassified. This formatting © 2006 Medical Education Division, Brookside Associates, Ltd. All rights reserved.

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