Sunday, March 14, 2021

Peritoneal Irritation Case File

Posted By: Medical Group - 3/14/2021 Post Author : Medical Group Post Date : Sunday, March 14, 2021 Post Time : 3/14/2021
Peritoneal Irritation Case File
Eugene C. Toy, MD, Lawrence M. Ross, MD, PhD, Han Zhang, MD, Cristo Papasakelariou, MD, FACOG

An 18-year-old man is seen in the emergency department complaining of a “stomachache all over” and fever. He reports that 2 days ago, he had some soreness around the umbilicus, and then yesterday, the pain seemed to go to the right lower abdomen. Today, he complains of pain throughout the abdomen with fever and chills. He is not hungry. On examination, his temperature is 102°F, heart rate is 110 beats/min, and blood pressure is 130/90 mmHg. An abdominal examination reveals a distended abdomen. There are hypoactive bowel sounds on auscultation. The patient has generalized tenderness throughout the abdomen with involuntary guarding and rebound tenderness.

 What is the most likely diagnosis?
 What is the explanation for the change in location of the pain?
 What is the mechanism for the rebound tenderness?


Peritoneal Irritation
Summary: An 18-year-old man is seen for a progression of abdominal pain that began periumbilically, and then spread to the right lower quadrant, followed by generalized abdominal pain. He has fever, hypoactive bowel sounds, and involuntary guarding with rebound tenderness.

• Most likely diagnosis: Acute appendicitis, likely ruptured with generalized peritonitis.

• Explanation for change in location of pain: Originally, the pain from the appendicitis is referred to the umbilicus (visceral sensation), and then as the appendicitis becomes more acute and inflamed, the parietal peritoneum is affected and localizes to the right lower quadrant. Finally, the perforation leads to purulent material throughout the abdominal cavity with peritoneal irritation causing rebound tenderness.

• Mechanism for rebound tenderness: Quick release of pressure from the clinician’s hand leads to “rebounding” of the peritoneum, which, if inflamed, will cause pain.

This young man has the typical presentation of acute appendicitis that has progressed initially from engorgement (visceral pain) to inflammation affecting the parietal peritoneum (somatic pain), and finally to frank rupture of the appendix. Pus is released into the entire peritoneal cavity, leading to generalized pain and rebound tenderness. Visceral pain is typically within the walls of hollow organs and stimulated by stretching, distension, or contractions. It is poorly localized and usually felt in the midline. In this case the distension of the appendix leads to a poorly defined periumbilical pain. Further questioning may lead to a description of deep, dull aching or cramping. When the appendix becomes inflamed and the inflammation on its surface touches the parietal peritoneum, there is more localized pain. This pain is described as sharper, aggravated by stimulation of the parietal peritoneum such as movement, coughing, or walking. In eliciting rebound tenderness, the physician presses deep on the abdomen and then quickly removes the hand (or pressure), and the patient experiences a sudden onset of pain on release of the pressure, rather than from the pressure itself. This is due to peritoneal irritation, and the pain occurs because the peritoneum rebounds back, activating sensory fibers, when the pressure is suddenly released. Other indications of peritoneal irritation include pain on percussion of the abdomen.


1. Be able to define the differences between visceral peritoneum, parietal peritoneum, and a mesentery (peritoneum ligament or omentum)
2. Be able to define the peritoneal cavity, greater sac, lesser sac, and their contents (if any)
3. Be able to describe the differences in the sensory innervation of the visceral versus parietal peritoneum

REFERRED PAIN: Perception of pain superficially that is arising from a deeper, often distant source

The peritoneum consists of a thin serous membrane composed of a simple squamous epithelium called mesothelium, and a thin layer of loose connective tissue, rich in elastic fibers. The peritoneum is divided into a portion that lines the inferior surface of the diaphragm and the abdominal and pelvic walls, the parietal peritoneum, and the portion that covers all or a part of the abdominopelvic viscera, the visceral peritoneum (see Figure 56-1).

Another peritoneal structure is a double-peritoneal sheet with a connective core, called a mesentery. The connective tissue core may contain a large amount of fat, serving the body as a major storage site for fat. Blood vessels and nerves passing to and from the viscera and the posterior body region are also located within the connective tissue core. These double-peritoneal sheets are sometimes termed ligament or omentum.

The space between the parietal and visceral peritoneum is called the peritoneal cavity. The peritoneum produces a small amount of serous fluid called peritoneal fluid, which lubricates movement of the viscera suspended in the peritoneal cavity. The peritoneal cavity in subdivided into the large greater sac extending from the diaphragm superiorly, to the pelvic cavity inferiorly. A smaller lesser sac or omental bursa is found posterior to the liver and stomach. It communicates with the greater sac via the omental foramen (epiploic foramen of Winslow). The peritoneal cavity of the male is closed, but that of the female is open to the outside via the uterine tubes, uterus, and vagina.

The sensory innervation of the peritoneum is important clinically. The parietal peritoneum of the central underside of the diaphragm (derived from the septum transversum) receives its sensory innervation from the phrenic nerve (C3−C5). Innervation of the peritoneum on the underside of the diaphragm’s periphery is provided by spinal nerves T6 through T12. Innervation of the peritoneum lining the

Peritoneal Irritation anatomy

Figure 56-1. (a) Relationship between the mesentery and the peritoneal organs; (b) axial cross section of the peritoneum and mesentery. [Reproduced, with permission, from Morton DA, Foreman KB, Albertine KH. The Big Picture: Gross Anatomy. New York: McGraw-Hill, 2011:99 (Figure 8-1B and C).]

abdominal wall is provided by spinal nerve T6 through T12 and L1, while the peritoneum lining the pelvic wall is innervated by the obturator nerve (L2−L4). These somatic nerves providing sensory innervation to the parietal peritoneum are essentially sensitive to pain, touch, temperature, and pressure. This latter sensation is the basis of rebound tenderness from an already irritated peritoneum. These somatic nerves from the parietal peritoneum provide an intense, well-localized sensation. Sensory innervation from the visceral peritoneum covering most of the abdominopelvic organs, as well as their mesenteries, are not sensitive to touch, temperature, or pressure, but are sensitive to ischemia, stretching, or tearing, such as from a swollen or distended organ. These visceral afferent nerves are described as being part of the autonomic nervous system (ANS), and travel back to the spinal cord via the sympathetic portion of the ANS. They convey a dull, poorly localized sensation.

Referred pain means the sensation of pain at a site different from its original source. Pain sensation originating from a gastrointestinal organ is often perceived at or near the midline. This is attributed to the fact that these organs are midline in origin. The clinically important referred pain involves both the visceral and somatic sensory nerves. For example, the visceral afferent fibers from the stomach travel
to the spinal cord via the greater splanchnic nerves to reach the T5 through T9 levels of the spinal cord. Pain from the stomach is often perceived initially and somewhat vaguely at the epigastric midline, which, in turn, is supplied by spinal nerves T5 through T9. Visceral afferent fibers from the appendix enter the spinal cord at approximately the T10 level, and pain from a distended appendix is initially perceived at the periumbilical region which is typically supplied by the T10 spinal nerve. If the organ is inflamed and becomes distended, as is often the case, the adjacent parietal peritoneum may also became irritated. In such instances, the initially vague periumbilical discomfort can shift to a well-localized, intense right lower quadrant pain from the appendix itself. This well-localized pain may be accompanied by muscular rigidity or “guarding,” which is a body reflex, while attempting to reduce peritoneal movement, which, in turn, may produce pain.

The mechanism for referred pain is not fully understood. It may be more complex than entry of sensory nerve fibers into the central nervous system (CNS) at a common spinal cord level (e.g., T10 for the periumbilical region and the appendix itself). For example, a common pathway that courses superiorly to the brain from the spinal cord may also be involved in the conscious perception of pain.

56.1 During a dissection, you inform your colleague that the surface of the peritoneum covering the stomach is composed of
    A. Simple squamous epithelium
    B. Simple cuboidal epithelium
    C. Simple columnar epithelium
    D. Stratified squamous epithelium
    E. Transitional epithelium

56.2 You point to the colon with your probe, and ask your colleague “What tissue am I touching?”
    A. Visceral pleura
    B. Parietal pleura
    C. Mesentery
    D. Parietal peritoneum
    E. Visceral peritoneum

56.3 You ask your dissection colleague “What spinal nerves innervate the peritoneum on the underside of the central region of the diaphragm?”
    A. C3 through C5
    B. T5 through C9
    C. T6 through T12
    D. T10
    E. L2 through L4
56.4 Continuing your discussion with your dissection colleague, you ask “Which spinal nerve innervates the umbilical region?”
    A. T4 through T6
    B. T8
    C. T10
    D. T12
    E. L1

56.1 A. The peritoneal epithelium is the simple squamous type.

56.2 E. The abdominal organs are covered in whole or in part by visceral peritoneum.

56.3 A. The sensory impulses of the central underside of the diaphragm are sent to segments C3 through C5 of the spinal cord, from which the phrenic nerve arises.

56.4 C. The dermatome at the level of the umbilicus is T10, and its sensory fibers are a part of the T10 spinal nerve.

 The epithelium of the peritoneum is simple squamous, called mesothelium.
 Parietal peritoneum lines the underside of the diaphragm and abdominopelvic walls and, if irritated, is characterized by intense, well-localized pain.
 Visceral peritoneum covers some, if not the entire, surface of abdominopelvic organs and is characterized by vague, dull pain if irritated.
 The sensory fibers of the appendix and umbilicus reach the T10 level of the spinal cord.
 Muscle rigidity or guarding helps reduce the pain from the parietal peritoneum by reducing movement.


Gilroy AM, MacPherson BR, Ross LM. Atlas of Anatomy, 2nd ed. New York, NY: Thieme Medical Publishers; 2012:150−155. 

Moore KL, Dalley AF, Agu AMR. Clinically Oriented Anatomy, 7th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:159, 217−218. 

Netter FH. Atlas of Human Anatomy, 6th ed. Philadelphia, PA: Saunders; 2014: plates 263−267.


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