Urinalysis

One study of 500 patients with acute appendicitis revealed that approximately one third reported urinary symptoms, most commonly dysuria or right flank pain. One in 7 patients had pyuria greater than 10 WBC per high power field, and 1 in 6 patients had greater than 3 RBC per high power field. Thus, the diagnosis of appendicitis should not be dismissed due to the presence of urologic symptoms or abnormal urinalysis.

C-reactive protein test

C-reactive protein (CRP) is an acute-phase reactant synthesized by the liver in response to infection or inflammation. A rapid assay is widely available.
Several prospective studies (Thimsen 1989, Albu 1994, de Carvalho 2003) have shown that, in adults who have had symptoms for longer than 24 hours, a normal CRP level has a negative predictive value of 97-100% for appendicitis.
In a 1989 study of 70 patients, Thimsen et al noted that a normal CRP level after 12 hours of symptoms was 100% predictive of benign, self-limited illness.⁷
Multiple studies have examined the sensitivity of CRP alone for the diagnosis of appendicitis in patients selected to undergo appendectomy.

• Gurleyik et al, in 1995, found that 87 of 90 patients with histologically proven appendicitis had an elevated CRP, a sensitivity of 96.6%.
• Shakhetrah, in 2000, found that 85 of 89 patients with histologically proven appendicitis had an elevated CRP, a sensitivity of 95.5%.
• Asfar et al, in 2000, completed a prospective double blind study of 78 patients undergoing appendectomy and found that CRP had a sensitivity of 93.6%.
• Erkasap et al, in 2000, prospectively studied the more relevant group of 102 adult patients with RLQ pain, 55 of whom proceeded to appendectomy. In this group, the sensitivity of CRP was 96%.

Investigators have also studied the ability of combinations of WBC and CRP to reliably rule out the diagnosis of appendicitis.

• Gronroos, in 1999, studied 300 patients operated for suspected appendicitis (200 positive, 100 negative) and found that WBC or CRP was abnormal in all 200 patients with appendicitis.
• Ortega-Deballon et al, in 2008, prospectively studied patients referred to a surgeon for RLQ pain and found that normal WBC and CRP had a negative predictive value of 92.3% for the presence of appendicitis.
• Yang, in 2006, retrospectively studied 897 patients who underwent appendectomy (740 with appendicitis, 157 without) and found that only 6 of 740 patients with appendicitis had WBC <10,500 cells/mm³ AND neutrophilia <75%, AND a normal CRP. This yields a sensitivity of 99.2% for the "triple screen".

Some studies have examined the sensitivity of combined WBC and CRP in the subpopulation of patients older than 60 years.

• Gronroos, in 1999, studied 83 patients older than 60 years who underwent appendectomy (73 found to have appendicitis) and found that no patient with appendicitis had both normal WBC and CRP.
• Yang et al, in 2005, retrospectively studied 77 patients older than 60 years with histologically proven appendicitis and found that only 2 had a normal "triple screen."

Several studies have examined the accuracy of CRP and WBC in the subpopulation of pediatric patients with suspected appendicitis.

• Gronroos, in 2001, studied 100 children with pathology-proven appendicitis and found that both WBC and CRP were normal in 7 of the 100 patients.
• Mohammed, in 2004, prospectively studied 216 children admitted for suspected appendicitis and found triple screen sensitivity and negative predictive value of 86% and 81%, respectively.
• Stefanutti et al, in 2007, prospectively studied more than 100 children undergoing surgery for suspected appendicitis and found that either WBC or CRP was elevated in 98% of those with pathology-proven appendicitis (CI, 95.3-100%).

CRP is nonspecific and does not distinguish between various types of infection or inflammation.

Workup

Laboratory Studies

Complete blood cell count
Studies consistently show that 80-85% of adults with appendicitis have a WBC count greater than 10,500 cells/mm³. Neutrophilia greater than 75% occurs in 78% of patients. Fewer than 4% of patients with appendicitis have a WBC count less than 10,500 cells/mm³ and neutrophilia less than 75%.
Dueholm et al, in 1989, further delineated the relationship between WBC count and the likelihood of appendicitis by calculating likelihood ratios for defined intervals of the WBC count.

Causes

• Obstruction of the appendiceal lumen usually precipitates appendicitis.
• The most common causes of luminal obstruction are fecaliths and lymphoid follicle hyperplasia.
• Fecaliths form when calcium salts and fecal debris become layered around a nidus of inspissated fecal material located within the appendix.
• Lymphoid hyperplasia is associated with a variety of inflammatory and infectious disorders including Crohn disease, gastroenteritis, amebiasis, respiratory infections, measles, and mononucleosis.
• Obstruction of the appendiceal lumen has less commonly been associated with parasites (eg, Schistosomes species, Strongyloides species), foreign material (eg, shotgun pellet, intrauterine device, tongue stud, activated charcoal), tuberculosis, and tumors.

Clinical

History

• Variations in the position of the appendix, age of the patient, and degree of inflammation make the clinical presentation of appendicitis notoriously inconsistent.
• It is important to remember that the position of the appendix is variable. Of 100 patients undergoing 3-D multidetector CT, the base of the appendix was located at McBurney's point in only 4% of patients. In 36% of patients, the base was within 3 cm of McBurney's point; in 28%, it was 3-5 cm from McBurney's point; and, in 36% of patients, the base of the appendix was more than 5 cm from McBurney's point.
• In addition, patients with many other disorders present with symptoms similar to those of appendicitis. Examples include the following:
• Pelvic inflamatory disease(PID) or tubo-ovarian abscess
• Endometriosis
• Ovarian cyst or torsion
• Ureterolithiasis and renal colic
• Degenerating uterine leiomyomata
• Diverculitis
• Crohn disease
• Colonic carcinoma
• Rectus sheath hematoma
• Cholecystitis
• Bacterial enteritis
• Mesenteric adenitis
• Omental torsion
• The classic history of anorexia and periumbilical pain followed by nausea, right lower quadrant (RLQ) pain, and vomiting occurs in only 50% of cases.
• Migration of pain from the periumbilical area to the RLQ is the most discriminating feature of the patient's history. This finding has a sensitivity and specificity of approximately 80%. Positive likelihood ratio is 3.18 (2.41-4.21), and negative likelihood ratio is 0.5 (0.42-0.59).
• When vomiting occurs, it nearly always follows the onset of pain. Vomiting that precedes pain is suggestive of intestinal obstruction, and the diagnosis of appendicitis should be reconsidered.
• Nausea is present in 61-92% of patients; anorexia is present in 74-78% of patients. Neither finding is statistically different from findings in ED patients with other etiologies of abdominal pain.
• Diarrhea or constipation is noted in as many as 18% of patients and should not be used to discard the possibility of appendicitis.
• Duration of symptoms is less than 48 hours in approximately 80% of adults but tends to be longer in elderly persons and in those with perforation. Approximately 2% of patients report duration of pain in excess of 2 weeks.
• A history of similar pain is reported in as many as 23% of cases. A history of similar pain, in and of itself, should not be used to rule out the possibility of appendicitis.
• An inflamed appendix near the urinary bladder or ureter can cause irritative voiding symptoms and hematuria or pyuria. Cystitis in male patients is rare in the absence of instrumentation. Consider the possibility of an inflamed pelvic appendix in male patients with apparent cystitis.
• Also consider the possibility of appendicitis in pediatric or adult patients who present with acute urinary retention.

Physical

• RLQ tenderness is present in 96% of patients, but this is a nonspecific finding. Rarely, left lower quadrant (LLQ) tenderness has been the major manifestation in patients with situs inversus or in patients with a lengthy appendix that extends into the LLQ.
• The most specific physical findings are rebound tenderness, pain on percussion, rigidity, and guarding.
• The Rovsing sign (RLQ pain with palpation of the LLQ) suggests peritoneal irritation in the right lower quadrant precipitated by palpation at a remote location.
• The obturator sign (RLQ pain with internal and external rotation of the flexed right hip) suggests that the inflamed appendix is located deep in the right hemipelvis.
• The psoas sign (RLQ pain with extension of the right hip or with flexion of the right hip against resistance) suggests that an inflamed appendix is located along the course of the right psoas muscle.
• These signs are present in a minority of patients with acute appendicitis. Their absence never should be used to rule out appendiceal inflammation.
• Dunphy's sign (sharp pain in the RLQ elicited by a voluntary cough) may be helpful in making the clinical diagnosis of localized peritonitis. Similarly, RLQ pain in response to percussion of a remote quadrant of the abdomen, or to firm percussion of the patient's heel, suggests peritoneal inflammation.
• The Markle sign, pain elicited in a certain area of the abdomen when the standing patient drops from standing on toes to the heels with a jarring landing, was studied in 190 patients undergoing appendectomy and found to have a sensitivity of 74%.
• There is no evidence in the medical literature that the digital rectal examination (DRE) provides useful information in the evaluation of patients with suspected appendicitis; however, failure to perform a rectal examination is frequently cited in successful malpractice claims. In 2008, Sedlak et al studied 577 patients who underwent DRE as part of an evaluation for suspected appendicitis and found no value as a means of distinguishing patients with and without appendicitis.
• Male infants and children occasionally present with an inflamed hemiscrotum due to migration of an inflamed appendix or pus through a patent processus vaginalis. This is often initially misdiagnosed as acute testicular torsion.

Acute Appendicitis

Introduction
Background
Appendicitis is a common and urgent surgical illness with protean manifestations, generous overlap with other clinical syndromes, and significant morbidity, which increases with diagnostic delay. No single sign, symptom, or diagnostic test accurately confirms the diagnosis of appendiceal inflammation in all cases.
The surgeon's goals are to evaluate a relatively small population of patients referred for suspected appendicitis and to minimize the negative appendectomy rate without increasing the incidence of perforation. The emergency department clinician must evaluate the larger group of patients who present to the ED with abdominal pain of all etiologies with the goal of approaching 100% sensitivity for the diagnosis in a time-, cost-, and consultation-efficient manner.
Pathophysiology
Obstruction of the appendiceal lumen is the primary cause of appendicitis. An anatomic blind pouch, obstruction of the appendiceal lumen leads to distension of the appendix due to accumulated intraluminal fluid. Ineffective lymphatic and venous drainage allows bacterial invasion of the appendiceal wall and, in advanced cases, perforation and spillage of pus into the peritoneal cavity.
Frequency

United States

Appendicitis occurs in 7% of the US population, with an incidence of 1.1 cases per 1000 people per year. Some familial predisposition exists.

International

Incidence of appendicitis is lower in cultures with a higher intake of dietary fiber. Dietary fiber is thought to decrease the viscosity of feces, decrease bowel transit time, and discourage formation of fecaliths, which predispose individuals to obstructions of the appendiceal lumen.
Mortality/Morbidity
• The overall mortality rate of 0.2-0.8% is attributable to complications of the disease rather than to surgical intervention.
• Mortality rate rises above 20% in patients older than 70 years, primarily because of diagnostic and therapeutic delay.
• Perforation rate is higher among patients younger than 18 years and patients older than 50 years, possibly because of delays in diagnosis. Appendiceal perforation is associated with a sharp increase in morbidity and mortality rates.
Sex
The incidence of appendicitis is approximately 1.4 times greater in men than in women. The incidence of primary appendectomy is approximately equal in both sexes.
Age
• Incidence of appendicitis gradually rises from birth, peaks in the late teen years, and gradually declines in the geriatric years. The median age at appendectomy is 22 years.
• Although rare, neonatal and even prenatal appendicitis have been reported.
• The emergency department clinician must maintain a high index of suspicion in all age groups.