Chapter 34. Abdominal Pain

Abdominal pain is one of the most common presenting complaints in the primary care physician’s office and often a diagnostic dilemma for surgeons. Despite recent technologic advances, the diagnosis and treatment of chronic, recurrent abdominal pain remain a challenge. Pain is a subjective sensation that patients often find difficult to describe. By contrast with other areas of the body, the abdominal organs have poorly developed sensory systems that also may contribute to the patient’s difficulty when trying to describe and localize the pain. In the majority of clinical scenarios, no physical course is apparent and symptoms are transient. The purpose of pain is to protect the organ and the patient from injury. After the source of the pain is found, every effort should be made to control or eliminate it. In chronic pancreatitis or diffuse malignancy, for example, pain control may become as much a challenge as in instances where no underlying cause can be found.

For a patient to perceive pain, the autonomic nervous system must be intact. The anatomy and physiology of pain have been described in detail in previous chapters. Abdominal viscera are relatively insensitive to many stimuli compared with a more sensitive organ such as the epidermis. In addition to the relative paucity of sensory nerve endings, the same group of nerves may innervate several viscera. There are a few well-known nociceptive triggers in the abdominal cavity. These include abnormal distention or contraction of hollow organ walls, ischemia of the visceral musculature, direct action of chemical substances on the mucosa, formation of allogenic mediators, and traction or compression of ligaments, vessels, or mesentery. Pain patterns are not well differentiated as to their location or the cause. Nevertheless, there are some recognizable pain patterns, and a careful history often can lead to the correct diagnosis. The history and physical examination provide diagnosis in two thirds of clinical presentations. Laboratory and radiologic tests are important auxiliary tools for investigative workup. The invasiveness and cost-effectiveness of the proposed tests should always be considered.

There is either a physical (organic) or psychogenic (nonorganic) cause to pain, with one or more elements dominating. Abdominal pain can be classified by the duration of the symptoms, etiology, primary diagnosis, anatomic localization, and its response to treatment. It can be either acute or chronic; chronic pain being arbitrary, based on symptoms persisting for more then 6 months or after the healing process is completed. Some clinicians divide pain into nociceptive (somatic or visceral), neuropathic, psychogenic, or referred.

Visceral pain is transmitted from nociceptors found on the walls of the abdominal viscera via sympathetic (thoracic branches and lumbar splanchnic nerves synapsing in subsidiary plexuses: celiac, splenic, hepatic, aorticorenal, superior mesenteric, adrenal) and parasympathetic (vagus and nervi erigentes S2–4; motor and sensory) pathways. This pain is nonspecific because of wide divergence and relatively small number of afferent fibers innervating a large area with extensive ramification. Patients usually have difficulty localizing the source of pain and will describe it as aching, cramping, or burning that fluctuates in intensity. Visceral pain usually is paroxysmal, colicky, deep, squeezing, and diffuse. Still, today, a theoretical explanation for transduction and transmission of visceral pain is being used.

Centralistic and peripheralistic theories of pain are widely recognized. The centralistic theory is subdivided into the convergence projection and convergence facilitation views. The former states that visceral fibers with nociceptive input converge onto somatosensory spinal neurons, and that the viscerosomatic cells project through nociceptive pathways. The convergence facilitation theory focuses on the fact that visceral activation changes the excitation of multiple spinal units (including pain pathways) without direct activation of spinal neurons. The peripheralistic theory claims that vasoactive substances released into cutaneous and deep tissues lead to hyperalgesia and referred pain from these structures.

Differentiating somatic from referred pain can be accomplished by reviewing the patient’s history and selective blocks. Somatic pain tends to be more intense or sharp and is aggravated by movement. It is produced by the stimulation of nociceptors in the parietal peritoneum and intra-abdominal connective tissues. It is usually well localized and described as constant, aching, gnawing, and throbbing. It can be relieved by opiates and peripheral nerve blocks. Referred pain can be explained easily by our knowledge of the segmental distribution of the spinal nerves. The pain can be referred to remote areas of the body if visceral impulses enter the spinal cord at the same level as afferent nerves from another area. These impulses are mistakenly interpreted as pain initiating at the second site. In addition, the pain may spread cranially to adjacent segments. Lower lobe pneumonia may be associated with severe upper abdominal pain and even some associated guarding. This is the most frequently used example of referred pain (Fig. 34-1).

Examination of the patient with abdominal pain must be done through an organized approach. Description of current and previous disease (including psychiatric treatment) in conjunction with a social and family history will develop a picture of the pain and a presumptive diagnosis. A history of allergies and current medications must be elicited. Knowledge of the pain pattern and character is also important. Following this, the patient should be carefully examined. A useful algorithm is presented in Figures 34-2 and 34-3.

The patient can differentiate superficial abdominal pain easily. A local process in the abdominal wall usually causes it. Pain over the xiphoid or costal margins that is exacerbated by movement or touch often is attributable to costochondritis, a form of arthritis that usually responds to appropriate therapy with anti-inflammatory agents or intra-articular injections. Sharp, burning pain near a recently healed incision may indicate nerve irritation from surgical transection, entrapment in the healing tissue, or regeneration with neuroma formation. Pain originating in the abdominal wall frequently can be confirmed by Carnett’s test and obliterated by blocking the appropriate intercostal or paravertebral nerves. Block of the celiac plexus can be helpful in differentiating abdominal wall or genitourinary pain from intraabdominal visceral pain, because the plexus supplies all abdominal viscera except the rectum, sigmoid, bladder, and reproductive organs.

The more common deep abdominal pain is, by definition, either somatic or visceral (autonomic: sympathetic and parasympathetic). Somatic pain originates in the parietal peritoneum, the root of the mesentery, and is elicited in close proximity to the nociceptive source. It is intense, sharp, precisely localized, associated with external stimuli, and represented at the cortical levels. Severity is related to the intensity of stimulus. Visceral pain is described more often as a poorly localized, vague (can be colicky, cramping, squeezing, dull, aching) pain associated with internal factors. Sometimes the pain can be referred to another part of the body. It can be presented as diffuse midabdominal discomfort. The intensity of the stimulus is as essential as its quality (i.e., cutting or coagulating the bowels is painless, but distention will cause pain). It is a primarily reflex and can be represented at the cord levels. Sometimes severe, visceral pain may generate a secondary physiologic reaction mediated by the autonomic nervous system and manifested by nausea, vomiting, sweating, lightheadedness, and salivation

The pain from the stomach, pancreas, and hepatobiliary tree is referred to the epigastrium. Periumbilical localization occurs from the small bowel and right colon; the rest of the colon and the genitourinary organs cause pain that presents in the epigastrium. The common midline pain location is a result of the bilateral innervation of the abdominal organs from both sides of the spinal cord (Fig. 34-4).

To determine the source of the pain, it is important to assess its intensity, location (Fig. 34-5), and character. It is also important to note its onset, whether acute or insidious, and its temporal profile. The circumstances that intensify or alleviate the pain are significant. Relief with eating or antacids suggests ulcer disease or gastroesophageal reflux. Postprandial pain, depending on its location, character, and timing, could be biliary, ischemic, or associated with a more benign condition, such as lactose intolerance or irritable bowel syndrome. Seasonal patterns frequently are seen in ulcer disease and, occasionally, with regional enteritis. The pain of inflammatory bowel disease and irritable bowel syndrome may be relieved by defecation, whereas heat usually relieves pain of musculoskeletal origin. Posture, sudden movement, coughing, straining, and sneezing may worsen the pain from peritoneal irritation or of spinal origin. The abdomen is not exempt from psychogenic pain. This may be manifested as a component of irritable bowel syndrome. Although common, psychological pain should and does remain a diagnosis of exclusion.

Esophagus

Heartburn is the most common symptom referable to the esophagus. It is a burning or hot substernal discomfort that frequently moves up toward the neck, but it may be localized only to the epigastrium. Eating, bending down, lying down after eating, and occasionally vigorous exercise may precipitate it. It is not entirely clear whether heartburn is caused by the chemical irritation of acid or bile, or if secondary muscle spasm plays a role. Occasionally, the pain is described as being a heaviness or tightness in the chest, with secondary restricted respiration and subsequent shortness of breath, simulating myocardial ischemia. The shortness of breath may be caused by an intercostal muscle spasm mediated by spinal reflex arcs.

Usually, the pain from the esophagus is felt at the level of the lesion. In some patients, however, pain caused by a lesion in the lower third of the esophagus is felt in the throat or in the high retrosternal area. The opposite is uncommon. When heartburn is severe, such as that associated with an ulcerating or infiltrating process, esophageal pain can radiate into the back, between the shoulder blades.

Stomach and Duodenum

The character of pain from ulcer disease varies widely. Typically, it is located in the epigastrium. It may be a sharply localized burning or gnawing pain or just a vague discomfort occurring from ½ to 2 hours after eating. Occasionally, it occurs shortly before meals or on an empty stomach and it may wake the patient up in the early hours of the morning. Food or antacids relieve it. The pain may, at times, be more localized to the right or left upper quadrant. When the pain bores through into the back, it usually indicates a posterior duodenal wall ulcer with secondary irritation of, or penetration into, the pancreas. This pain usually is deep, persistent, poorly localized, and does not respond well to treatment. Unlike heartburn, ulcer pain frequently occurs in clusters; several weeks of daily pain may be followed by variably long pain-free intervals. There may be seasonal variation with the symptoms; that is, they may be worse during the spring and fall.

Pain from gastritis tends to be more persistent and may be more difficult to abolish. The associated nausea and vomiting may be particularly troublesome. As in heartburn, it is not known whether the pain is produced by acid irritation of the nerve endings in the ulcer bed or whether it is secondary to a spasm of antral or duodenal smooth muscle.

Epigastric pain occurring soon after eating, unrelieved by antacids, and with lack of periodicity does not necessarily exclude ulcer disease. Pyloric channel ulcers may present in such a manner, and unless there is associated postprandial vomiting, the diagnosis may not be made until frank gastric outlet obstruction occurs.

Small Intestine

As a rule, pain originating in the small intestine is periumbilical in location and crampy or colicky in nature. Jejunal lesions tend to be associated with pain in the left upper quadrant. Ileal pain tends to localize in the right lower quadrant, and it may result from abnormal bowel motility patterns. A lowered threshold to the pain of bowel distention or contraction also can cause it. A lesion obstructing the lumen of the bowel, such as regional enteritis or a malignant process, may be the precipitating factor.

The pain of irritable bowel syndrome frequently is chronic, and at times, it can be incapacitating. It is unusual, however, for it to wake the patient from sleep. The pain usually is in the lower abdomen, in either the right or left lower quadrants. Its description ranges from burning, sharp, and stabbing to dull. Most commonly, it is intermittent, but it may be constant, with superimposed acute attacks. The pain may remain localized or may migrate with time. Eating usually precipitates it; defecation or fasting tends to relieve it. Nausea, bloating, and dyspepsia frequently occur and may simulate peptic ulcer or biliary tract disease. A change in bowel habits is not a universal finding, but, classically, diarrhea alternates with constipation. Predominant diarrhea or constipation, however, can be part of the syndrome.

Pain from partial small bowel obstruction also occurs after meals. The closer the lesion is to the stomach, the earlier the pain occurs. Moreover, nausea and vomiting are more likely to occur when the lesion is close to the stomach. The pain frequently is described as crampy and comes in waves. Regional enteritis is suggested by localization of the discomfort to the right lower quadrant and associated diarrhea, fever, weight loss, or extraintestinal manifestations, such as arthritis and mouth ulcers. Significant weight loss and cachexia may suggest an underlying lymphoma or metastatic disease to the bowel. It may be several months before complete obstruction occurs. At this time, the diagnosis is more obvious. As in appendicitis, the initial pain may be a nonspecific discomfort, but as the underlying process develops and eventually involves the overlying peritoneum, the pain localizes and approximates the site of the underlying disease.

Postoperative adhesions frequently are blamed for chronic or recurrent abdominal pain. Before exploration is considered, definitive evidence of bowel obstruction using plain abdominal x-rays or angulation and proximal dilation of the bowel using a barium study should be documented.

Colon

Pain from the colon usually is poorly localized to the lower abdomen. However, an adenocarcinoma of the colon or diverticula of the colon with secondary microperforation and abscess formation may have localized symptoms overlying the area of disease. Pain from the rectosigmoid area, in addition to being in the left lower quadrant, may be located in the sacral area.

Pancreas, Liver, and Biliary Tract

Because the pancreas, liver, biliary tract, stomach, and duodenum share some of the same afferent neuropathways, it is easy to understand some of the difficulties involved in the differential diagnosis of chronic epigastric pain. Diseases of the pancreas, and, in particularly, pancreatic cancer, are the most difficult to diagnose. Pain resulting from pancreatic cancer usually signifies infiltration of the retroperitoneal area or celiac axis, or spread to surrounding organs. Some of the pain may be a result of pancreatic duct obstruction and surrounding pancreatitis. Tumors in the head of the pancreas cause pain that is more localized to the epigastrium or right upper quadrant. Those in the tail tend to cause pain in the left upper quadrant. Lesions in the body of the pancreas can cause the pain to radiate into the back. Back pain, alone, also can be a presenting symptom. Because pancreatic cancer is rarely resectable, the physician is able to treat only the symptoms. When the retroperitoneal celiac plexus is involved by the tumor, the anesthesiologist frequently is asked to guide and help manage the pain.

The pain of chronic pancreatitis, which is mainly a result of alcohol abuse, can be constant, debilitating, and frequently lead to drug abuse. The persistent inflammation of the pancreas causes some of the pain, as does the ductal distention secondary to ductal obstruction by creation of strictures. The pain may be dull or sharp, burning, and steady. It commonly radiates into the back. Superimposed, more acute attacks last from days to several weeks. Eating, moving, or lying down may aggravate the pain; sitting up or leaning forward may relieve it. In patients who are not surgical candidates, the anesthesiologist may be asked to intervene. Neurolytic celiac plexus block has been used to treat patients who have not responded to conservative or surgical therapies. It often is used as a last resort, because rendering the abdomen insensitive may allow future abdominal disease to be missed.

Placement of stents during endoscopic retrograde cholangiopancreatography was used initially to decompress a dilated biliary tree. Only recently, this technique has been used to decompress the pancreatic duct. Relief may occur if the dilated biliary (or pancreatic) duct was the cause of the pain. Both benign and malignant lesions are amenable to this technique.

Passing a stone or biliary tree dilation secondary to an obstruction usually causes biliary pain. Contrary to the commonly used term biliary colic, the pain tends to have a gradual onset. After it peaks, it tends to reach a plateau until again, hours later, it diminishes. An attack can last from several hours to a day or more. The pain characteristically is localized in the right upper quadrant and may radiate to the right shoulder and shoulder blade, but it also is felt commonly in the epigastrium, with radiation into the back. Vomiting occurs in most patients and may provide some relief. After an acute attack, residual soreness may persist for several days. Commonly, these symptoms occur after eating, but they may become constant if the common bile duct is impacted by a stone or infiltrated by a malignant process. Associated dyspepsia is common in approximately one quarter of all patients. It responds to antacids, further confusing its cause. The appearance of complicating cholangitis (with symptoms of fever and jaundice) usually leads quickly to the correct diagnosis.

The liver parenchyma is insensitive to pain, but relatively rapid distention of the liver capsule will initiate well-localized right upper quadrant pain. Acute processes such as viral hepatitis, alcoholic hepatitis, and cardiac decompensation with secondary liver congestion rarely may appear as right upper quadrant pain, but this pain does not evolve into a chronic complaint. Chronic, active hepatitis may follow a course of recurrent attacks of right upper quadrant pain. The pain usually is well localized and accompanied by worsening liver function tests.

Benign focal nodular hyperplasia or adenomas associated with the use of birth control pills may cause recurrent right upper quadrant discomfort or, occasionally, a dramatic crisis of severe abdominal pain and hypotension from a hemorrhage into the capsule or peritoneum. The recurrent warning pains probably are caused by small bleeding episodes into the lesions. Bleeding into or necrosis of malignant lesions in the liver causes similar pain, but this usually is accompanied by fever and jaundice. The pain may be well localized, sharp, and steady. Any movement producing friction between the liver surface and the ribs may exacerbate it. When sought, a bruit over the lesion may he identified in approximately 25% of patients.

Vascular Diseases of the Bowel

Although mainly asymptomatic, occlusive vascular disease may be associated with chronic, recurrent, dull paraumbilical or epigastric pain. The pain of intestinal angina begins approximately ½ hours after eating and lasts throughout digestion and absorption of the meal. Usually, at least two of the three major splanchnic vessels are affected by significant obstruction from atherosclerotic changes. It is postulated that the collateral supply is insufficient to meet the increased need during digestion, and this state of relative ischemia creates subsequent pain. Classically, this recurrent pain may create a fear of eating and can lead to severe weight loss. When patients with acute ischemia are questioned closely, retrospectively, they often will report postprandial abdominal discomfort preceding the acute event by weeks to months.

Superior mesenteric artery syndrome and celiac compression syndrome frequently are mentioned in the differential diagnosis of chronic abdominal pain, but their validity is controversial. Superior mesenteric artery syndrome is described as occurring in so-called asthenic patients or patients with significant weight loss. The postprandial epigastric pain, vomiting, and distention are believed to be caused by compression of the duodenum by the superior mesenteric artery. The pain of celiac compression syndrome is not necessarily related to meals. The celiac axis frequently has a high take-off and may be compressed by the median arcuate ligament of the diaphragm or by the tissue of the celiac ganglion. Whether bowel ischemia is the cause of the pain or whether the pain originates from the celiac ganglion also is unclear.

Abdominal aortic aneurysm usually presents more acutely, but a slowly expanding or leaking aneurysm may be associated with recurrent, dull midepigastric or back pain over several months. As with pancreatic pain, sitting up or leaning forward occasionally may relieve this pain. The pulsating, sometimes tender, mass can be palpated, and a bruit may be heard.

Peritoneum

The parietal peritoneum is well innervated by the branches of the spinal nerves, and, consequently, the pain perceived is well localized. Such pain frequently is associated with secondary muscle spasm of the overlying abdominal wall. The visceral peritoneum, however, has no pain receptors, and any pain that is generated is poorly defined. A malignant process most often causes chronic pain originating in the peritoneal cavity. Metastatic bowel or ovarian tumors and lymphoma are common. Mesothelioma is the most common primary tumor; teratoma, carcinoid, or sarcoma are much less common. The abdominal discomfort often is compounded by the presence of ascites, which distends the peritoneum further and causes more pain.

In young patients of Mediterranean descent who have chronic recurrent attacks of sudden diffuse or localized peritoneal pain, familial Mediterranean fever should be considered. Abdominal tenderness, fever, and arthritis are common. Despite feeling very ill, the patient recovers in several days and is well until the next attack.

Mesentery and Omentum

Recurrent localized or generalized abdominal pain in an older patient associated with the displacement of the stomach or bowel on x-ray studies should suggest a mesenteric or omental lesion. Fever, weight loss, nausea, vomiting, and a palpable tender mass may be associated with mesenteric panniculitis or retractile mesenteritis. Metastatic tumors to the mesentery are more common than primary lesions. The latter usually are fibromas, myomas, histiocytic or lipomatous tumors. Leiomyomas and leiomyosarcomas tend to involve the omentum.

Genitourinary System

The acute pain of renal colic or pyelonephritis is classic and easy to diagnose. The triad of hematuria, flank pain, and a palpable mass suggests renal cell carcinoma, but this triad occurs infrequently. The tumor often is diagnosed from systemic complaints (dull upper abdominal or flank pain may be included). Perinephric abscess, although uncommon, should be considered in a patient with a history of urinary tract infections or pyelonephritis. Typically, dull upper quadrant or flank discomfort is present, accompanied by malaise and low-grade fevers.

Gynecologic problems usually cause acute pain. Depending on the patient’s age, chronic lower abdominal pain, usually more localized to one of the lower quadrants, could be a presenting symptom of chronic pelvic inflammatory disease, uterine or ovarian cancer. The pain can be dull, steady, or crampy. The local irritation by the mass or inflammatory process can cause changes in the urine or bowel pattern.

Metabolic causes of chronic abdominal pain are rare but should always be sought, particularly when the usual diagnostic avenues have been exhausted. The hepatic porphyrias have many features in common, including their clinical presentation. Abdominal pain is the most prominent symptom. It is thought to result from autonomic neuropathy, which causes disturbances in gastrointestinal motility. Spasm and dilation of the bowel can cause severe pain. The frequent association of fever and leukocytosis mimics an inflammatory process. Although vomiting and constipation frequently are present, the abdomen is soft, without marked tenderness. These attacks may last from days to weeks. Fasting, infections, the menstrual cycle, and drugs whose metabolism involves the hemoproteins of cytochrome P-450 are often the precipitating factors. Such drugs include alcohol, barbiturates, anticonvulsants, estrogens, and contraceptives. Knowledge of so-called safe or probably safe drugs may be useful to the clinician treating the pain. Drugs that are considered safe include morphine and related opiates, which may be required to treat the pain in an acute attack.

In the United States, lead poisoning mainly is encountered in children. Although anemia, peripheral neuritis, and encephalopathy complete the picture, the young patient may have only lead colic, sometimes called painter’s cramps. Severe, migrating, poorly localized guarding and rigidity of the abdominal wall should raise the suspicion of an acute intraabdominal event that may accompany crampy abdominal pain.

When in a hemolytic crisis, a patient with paroxysmal nocturnal hemoglobinuria may have substernal, lumbar, or abdominal pain, in addition to generalized weakness. The pain may be colicky and last for several days. The abdomen may be tender, with some guarding and even a rebound phenomenon. Venous thrombosis occurs with increased frequency in these patients. It always should be considered if a sudden increase in liver size accompanies these attacks, suggesting thrombosis involving the portal system.

Hyperparathyroidism has been called the syndrome of bones, stones, and groans. Associated peptic ulcer disease or pancreatitis usually causes the abdominal pain.

The lightening-sharp abdominal pain of tabes mainly is associated with syphilis, but it also may occur with diabetes and meningeal tumors. This is a radicular syndrome resulting from damage to the large posterior lumbosacral roots.

The diagnosis of chronic recurrent abdominal pain often can be a challenge to both the therapeutic and diagnostic abilities of the involved physician. Unfortunately, many patients with this type of pain undergo multiple surgical procedures without any significant findings. Good knowledge of the underlying anatomy and pain patterns should make the diagnosis and subsequent treatment easier (Figure 34-6).

The abdomen is the third most common site of pain in psychiatric patients. Diagnosis of psychological pain can be made based on exclusion criteria. There are some signs that can be helpful or supportive. Suspicion is raised when location, timing, quality, and distribution of symptoms do not relate to pathophysiologic patterns. There is often marked discrepancy between reported severity of pain and presented behavior. The patient sometimes reports pain in other parts of body and may have a history of many negative diagnostic workups for various complaints. The onset of pain may have an obvious relationship to a stressful event.

Most of this chapter has dealt with the diagnosis of abdominal pain syndromes. When a treatable disorder is identified, appropriate therapy should be instituted. A simplified algorithm was presented at the beginning of this chapter (see Figs. 34-2, 34-3). Unfortunately, in many patients with chronic abdominal pain, a specific diagnosis is not identified despite an extensive workup. In other patients, a condition is diagnosed, but conventional methods fail to treat the disease and pain. Nerve blocks can be helpful in treating acute and chronic abdominal pain (Table 34-1). Nonspecific methods, such as antidepressants, stress reduction techniques, and behavioral approaches, often are useful in treating these difficult problems.