Acute Appendicitis Case File

Acute Appendicitis Case File

Eugene C. Toy, MD, Lawrence M. Ross, MD, PhD, Han Zhang, MD, Cristo Papasakelariou, MD, FACOG

CASE 21

An 18-year-old male college student complains of 12-h abdominal pain that began around his umbilicus but then shifted to the right lower quadrant (RLQ) and right side. He indicates that he has been nauseous over the past several hours. His temperature is 99.4°F. On physical examination, there is mild abdominal tenderness, particularly in the RLQ, but also on the right side. The laboratory analysis of the urine is normal.

⯈ What is the most likely diagnosis?

⯈ What accounts for the shift in location of the pain?

ANSWER TO CASE 21:

Acute Appendicitis

Summary: An 18-year-old man complains of 12-h abdominal pain that is initially periumbilical and then migrates to the RLQ. He has some nausea and a low-grade fever. The abdomen is tender in the RLQ and right lateral region. The urinalysis is normal.

• Most likely diagnosis: Appendicitis, possibly retrocecal.

• Cause of shift in location of pain: Pain initially irritates the visceral peritoneum, is referred to the periumbilical area, and then localizes to RLQ as the appendicitis worsens and inflames the parietal peritoneum.

CLINICAL CORRELATION

This college student’s complaints are suspicious for appendicitis. The appendix is a small diverticulum that arises from the cecum and is typically free in the peritoneal cavity. Not infrequently, however, it is retrocecal in location and causes right-side or flank tenderness and very few peritoneal signs. Initially, the abdominal pain is vaguely and generally located to the periumbilical region, but with time, it becomes sharper and precisely located to the RLQ. Nausea is common but presents after the onset of pain. Men and women are equally affected by appendicitis, but the diagnosis is usually more straightforward in men. A serum leukocyte count may be helpful. Ultimately, the suspicion is a clinical one, and diagnostic laparoscopy is undertaken to visualize the appendix. If appendicitis is confirmed, surgery is indicated.

APPROACH TO:

The Large Bowel

OBJECTIVES

1. Be able to describe the anatomy of the appendix and large intestine

2. Be able to describe the mechanism for referred pain

3. Be able to describe the general anatomic pattern for abdominal pain

DEFINITIONS

APPENDICITIS: Inflammation of the appendix that is often associated with a fecalith, a small piece of stool that occludes the proximal appendix

REFERRED PAIN: Pain that originates from a deep structure that is perceived at the surface of the body, often at a different location

DISCUSSION

The typical position of the appendix can be approximated at a point (McBurney) one-third of the way along a line drawn from the right anterior superior iliac spine to the umbilicus. The appendix is an elongated diverticulum that arises from the cecum inferior to the ileocecal junction (Figure 21-1). The three longitudinal smooth muscle bands characteristic of the cecum and colon, the teniae coli, can be traced inferiorly to the posteromedial origin of the appendix from the cecum. The appendix lies in the margin of a small triangular mesentery, the mesoappendix, within which the appendicular artery (a branch of the ileocolic artery) is also found. The posterior surface of the cecum is often covered with visceral peritoneum, creating a retrocecal recess. In close to 66 percent of individuals, the appendix

is retrocecal in position and is found in this recess. In almost 33 percent of individuals, the appendix is free and extends inferiorly toward or over the pelvic brim. The cecum and the appendix can lie at higher or lower positions relative to the McBurney point as a result of faulty embryonic gut rotation.

The large intestines are characterized by the presence of teniae coli, haustra, omental appendices, and their large diameter. The cecum is the pouchlike first part of the large intestines into which the ileum opens and the appendix arises. It is continuous superiorly with the ascending colon, which is the shortest segment of colon, is retroperitoneal (lacks a mesentery), is continuous with the transverse colon at the right colic (hepatic) flexure, and is supplied by the ileocolic and right colic branches of the superior mesenteric artery (SMA). The transverse colon is the longest segment of colon, begins at the right colic flexure, and is continuous with the descending colon at the more superiorly positioned left colic (splenic) flexure.

Figure 21-1. Cecal folds and fossae. (Reproduced, with permission, from Lindner HH. Clinical Anatomy. East Norwalk, CT: Appleton & Lange, 1989:361.)

It is intraperitoneal, as it is suspended by its mesentery, the transverse mesocolon. The middle colic artery branch of the SMA lies within the mesentery. The descending colon is retroperitoneal, continuous with the sigmoid colon near the left iliac crest, and is supplied by the left colic artery, a branch of the inferior mesenteric artery (IMA). The sigmoid colon is suspended by its mesentery, the sigmoid mesocolon, in which its blood supply, the several sigmoidal arteries, are found. The sigmoid colon ends at the rectosigmoid junction, which lies at the S3 vertebral level. The arteries that supply the colon are connected by continuous arterial anastomoses called the marginal arteries.

The initial vague, poorly localized pain of appendicitis results from stretching of the visceral peritoneum secondary to inflammation of the organ. The cell bodies of the visceral afferent nerve fibers from the appendix lie in the dorsal root ganglia and enter the spinal cord at levels T8 through T10. Sensory fibers from the umbilicus enter the spinal cord at T10. The brain misinterprets (refers) the pain from the appendix as arising from the umbilical and nearby abdominal wall. This is called referred pain. As the inflammatory process progresses, adjacent parietal peritoneum is typically irritated, and the pain shifts to the actual location of the appendix in the RLQ. The parietal peritoneum is innervated by somatic sensory nerve fibers and, when irritated, produces sharp, well-localized pain sensation. If the appendix is retrocecal, the parietal peritoneum of the posterior abdominal wall is irritated, resulting in side or flank tenderness.

Pain originating from foregut-derived organs and supplied by the celiac artery is generally perceived in the epigastric region. Pain from midgut-derived organs supplied by the SMA is perceived in the periumbilical region, and pain in the infraumbilical region arises from hindgut organs (IMA).

COMPREHENSION QUESTIONS

21.1 You are at surgery for the removal of a suspected appendicitis, but the appendix is not visible. The appendix is likely to be which of the following?

A. Anticecal

B. Paracecal

C. Paracolic

D. Retrocecal

E. Retrocolic

21.2 Which of the following techniques could you use to precisely locate the appendix?

A. Locate a region devoid of haustra

B. Trace the right collect artery

C. Trace the ileocolic artery

D. Trace the teniae (taeniae) coli on the cecum

E. Examine the pelvic cavity

21.3 A patient with infraumbilical pain is likely to have a disorder of which organ?

A. Appendix

B. Ascending colon

C. Ileum

D. Stomach

E. Sigmoid colon

ANSWERS

21.1 D. The appendix is retrocecal in position in almost 66 percent of the population.

21.2 D. The three teniae coli converge at the base of the appendix on the cecum.

21.3 E. Infraumbilical pain typically arises from hindgut-derived structures such as the sigmoid colon.

ANATOMY PEARLS

⯈ The appendix typically lies at the McBurney point and is retrocecal in about 66 percent of the population.

⯈ The SMA and IMA anastomose with each other through the marginal artery.

⯈ The initial referred pain of appendicitis is to the periumbilical region.

References

Gilroy AM, MacPherson BR, Ross LM. Atlas of Anatomy, 2nd ed. New York, NY: Thieme Medical Publishers; 2012:162−163. 

Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy, 7th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:247−249, 259−260. 

Netter FH. Atlas of Human Anatomy, 6th ed. Philadelphia, PA: Saunders; 2014: plates 273−276, 303.

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