Abdominal Pain¶

Chapter 16 | Part 2: Cardinal Manifestations and Presentation of Diseases

KEY CLINICAL POINTS¶

Acute abdominal pain requires distinguishing conditions needing urgent surgical intervention from those manageable nonoperatively
Pain severity does not necessarily correlate with severity of underlying condition - catastrophic events may present with subtle symptoms
A detailed history and physical examination are critically important for focusing differential diagnosis
Metabolic, neurogenic, and referred pain from extraabdominal sources must always be considered when abdominal pain etiology is obscure
Immunocompromised patients present unique diagnostic challenges with atypical presentations and unusual pathogens

1. DEFINITION & OVERVIEW¶

Correctly diagnosing acute abdominal pain is one of the most challenging clinical situations requiring significant clinical judgment. The most catastrophic of events may be heralded by the subtlest of symptoms and signs. The clinician must distinguish conditions requiring urgent intervention from those best managed nonoperatively. A meticulously executed, detailed history and physical examination are critically important for focusing the differential diagnosis and allowing diagnostic evaluation to proceed expeditiously.

Key Components of the Patient's History¶

Historical Element	Clinical Relevance
Age	Influences differential diagnosis priorities
Time and mode of onset of pain	Sudden vs gradual onset suggests different etiologies
Pain characteristics	Quality, intensity, pattern (constant vs colicky)
Duration of symptoms	Acute vs chronic presentations
Location of pain and sites of radiation	Helps localize pathology
Associated symptoms and their relationship to pain	Temporal relationships are diagnostically important
Nausea, emesis, and anorexia	Common accompaniments of abdominal pathology
Diarrhea, constipation, or other changes in bowel habits	Suggests GI tract involvement
Menstrual history	Essential in female patients of reproductive age

1.1 Clinical Significance¶

A diagnosis of 'acute or surgical abdomen' is not acceptable because of its often misleading and erroneous connotations. Although most patients presenting with acute abdominal pain will have self-limited disease processes, pain severity does not necessarily correlate with the severity of the underlying condition. The most obvious 'acute abdomens' may not require operative intervention, but the mildest of abdominal pain could indicate serious pathology.

1.2 Most Common Causes on Admission¶

The most common causes of abdominal pain on hospital admission are: (1) Nonspecific abdominal pain, (2) Acute appendicitis, (3) Pain of urologic origin, and (4) Intestinal obstruction.

2. ETIOLOGY & PATHOPHYSIOLOGY¶

Abdominal pain can originate from multiple mechanisms including inflammation of the parietal peritoneum, obstruction of hollow viscera, vascular disturbances, abdominal wall pathology, referred pain from extraabdominal sources, metabolic causes, and neurogenic causes.

Important Causes of Abdominal Pain¶

Category	Causes
Parietal Peritoneal Inflammation	Bacterial contamination (perforated appendix, perforated viscus, PID); Chemical irritation (perforated ulcer, pancreatitis, Mittelschmerz)
Mechanical Obstruction of Hollow Viscera	Small or large intestine obstruction; Biliary tree obstruction; Ureteral obstruction
Vascular Disturbances	Embolism or thrombosis; Vascular rupture; Pressure or torsional occlusion; Sickle cell anemia
Abdominal Wall	Distortion or traction of mesentery; Trauma or infection of muscles
Distension of Visceral Surfaces	Hemorrhage; Hepatic or renal capsule distension
Inflammation	Appendicitis; Typhoid fever; Neutropenic enterocolitis (typhlitis)
Cardiothoracic (Referred)	Acute MI; Myocarditis/endocarditis/pericarditis; CHF; Pneumonia (especially lower lobes); Pulmonary embolus; Pleurodynia; Pneumothorax; Empyema; Esophageal disease
Genitalia (Referred)	Torsion of testis
Metabolic Causes	Diabetes; Uremia; Hyperlipidemia; Hyperparathyroidism; Acute adrenal insufficiency; Familial Mediterranean fever; Porphyria; C1 esterase inhibitor deficiency (angioneurotic edema)
Neurologic/Psychiatric	Herpes zoster; Tabes dorsalis; Causalgia; Radiculitis from infection or arthritis; Spinal cord or nerve root compression; Functional disorders; Psychiatric disorders
Toxic Causes	Lead poisoning; Insect or animal envenomation; Black widow spider bites; Snake bites
Uncertain Mechanisms	Narcotic withdrawal; Heat stroke

2.1 Inflammation of the Parietal Peritoneum¶

Pain of parietal peritoneal inflammation is steady and aching in character, located directly over the inflamed area, and transmitted by somatic nerves. The intensity depends on the type and amount of material to which peritoneal surfaces are exposed in a given time period. Key principles: - Sudden release of sterile acidic gastric juice causes more pain than grossly contaminated pH-neutral feces - Enzymatically active pancreatic juice incites more pain and inflammation than sterile bile - Blood is normally only a mild irritant; response to urine is also typically bland - Bacterial contamination (e.g., PID, perforated distal intestine) causes low-intensity pain until bacterial multiplication releases significant inflammatory mediators - The rate at which inflammatory material irritates the peritoneum is important Characteristic features: - Pain invariably accentuated by pressure or changes in peritoneal tension (palpation, coughing, sneezing) - Patient characteristically lies quietly in bed, preferring to avoid motion (contrast with patient with colic who may be thrashing) - Tonic reflex spasm of abdominal musculature localized to involved body segment - Spasm intensity depends on nervous system integrity, location of inflammatory process, and rate of development - Spasm may be minimal over perforated retrocecal appendix or perforation into lesser peritoneal sac - Catastrophic abdominal emergencies may have minimal detectable pain or spasm in obtunded, seriously ill, debilitated, immunosuppressed, or psychotic patients

2.2 Obstruction of Hollow Viscera¶

Intraluminal obstruction classically elicits intermittent or colicky abdominal pain that is not as well localized as parietal peritoneal irritation. However, distention of a hollow viscus may also produce steady pain with only rare paroxysms. Small Bowel Obstruction: - Poorly localized, intermittent periumbilical or supraumbilical pain - As intestine dilates and loses muscular tone, colicky nature may diminish - With superimposed strangulating obstruction, pain may spread to lower lumbar region (traction on mesentery root) Colonic Obstruction: - Lesser intensity than small bowel obstruction - Commonly located in infraumbilical area - May radiate to lumbar region Biliary Tree Distention: - Produces steady rather than colicky pain (term 'biliary colic' is misleading) - Gallbladder: Right upper quadrant pain with radiation to right posterior thorax or right scapula tip; midline discomfort also common - Common bile duct: Epigastric pain that may radiate to upper lumbar region - Considerable variation is common; differentiation between gallbladder and common bile duct disease may be impossible - Gradual dilatation (e.g., carcinoma of pancreatic head) may cause no pain or only mild aching in epigastrium or RUQ Pancreatic Duct Distention: - Similar to common bile duct pain - Frequently accentuated by recumbency and relieved by upright position Urinary Bladder Obstruction: - Dull, low-intensity suprapubic pain - Restlessness without specific pain complaint may be only sign in obtunded patients Ureteral Obstruction: - Intravesicular ureter: Severe suprapubic and flank pain radiating to penis, scrotum, or inner aspect of upper thigh - Ureteropelvic junction: Pain near costovertebral angle - Remainder of ureter: Flank pain often extending into same side of abdomen

2.3 Vascular Disturbances¶

A frequent misconception is that pain due to intraabdominal vascular disturbances is sudden and catastrophic. While embolism/thrombosis of superior mesenteric artery or impending rupture of abdominal aortic aneurysm can cause diffuse, severe pain, this is not always the case. Superior Mesenteric Artery Occlusion: - May present with only mild continuous or cramping diffuse pain for 2-3 days before vascular collapse or peritoneal inflammation findings - Early discomfort caused by hyperperistalsis rather than peritoneal inflammation - Characteristic finding: Absence of tenderness and rigidity with continuous diffuse pain ('pain out of proportion to physical findings') in patients likely to have vascular disease Abdominal Aortic Aneurysm: - Pain with radiation to sacral region, flank, or genitalia signals possible rupturing aneurysm - Pain may persist over several days before rupture and collapse occur

2.4 Abdominal Wall Pain¶

Usually constant and aching. Movement, prolonged standing, and pressure accentuate discomfort and associated muscle spasm. Rectus sheath hematoma (most frequently with anticoagulant therapy) may present as a mass in lower quadrants. Simultaneous involvement of muscles in other body parts helps differentiate myositis from other processes.

2.5 Referred Pain in Abdominal Disease¶

Pain referred to the abdomen from thorax, spine, or genitalia presents diagnostic challenges. Diseases of the upper abdominal cavity (acute cholecystitis, perforated ulcer) may be associated with intrathoracic complications. Critical Dictum: The possibility of intrathoracic disease must be considered in every patient with abdominal pain, especially upper abdominal pain. Intrathoracic Diseases Masquerading as Abdominal Emergencies: - Myocardial infarction - Pulmonary infarction - Pneumonia - Pericarditis - Esophageal disease Differentiating Features of Thoracic Origin Pain: - Respiratory lag and decreased excursion more marked than with intraabdominal disease - Apparent abdominal muscle spasm diminishes during inspiration (persists throughout both respiratory phases if abdominal origin) - Palpation over referred pain area does not accentuate pain and may relieve it Diaphragmatic Pleuritis: - May cause right upper quadrant pain AND supraclavicular pain (distinguish from referred subscapular pain of acute biliary tree distention) Spinal Referred Pain: - Usually involves compression or irritation of nerve roots - Intensified by cough, sneeze, or strain - Associated with hyperesthesia over involved dermatomes Testicular/Seminal Vesicle Referred Pain: - Generally accentuated by slightest pressure on these organs - Dull, aching character and poorly localized

3. METABOLIC ABDOMINAL CRISES¶

Pain of metabolic origin may simulate almost any other type of intraabdominal disease. Several mechanisms may be at work.

3.1 Key Metabolic Conditions¶

Hyperlipidemia: - May be accompanied by pancreatitis, which can lead to unnecessary laparotomy unless recognized C1 Esterase Inhibitor Deficiency (Angioneurotic Edema): - Often associated with episodes of severe abdominal pain Familial Mediterranean Fever: - Abdominal pain is the hallmark (see Chapter 381) COVID-19: - Rarely, patients may present with severe abdominal pain in absence of pulmonary symptoms Porphyria and Lead Colic: - Usually difficult to distinguish from intestinal obstruction because severe hyperperistalsis is a prominent feature of both Uremia or Diabetes: - Pain is nonspecific - Pain and tenderness frequently shift in location and intensity - Diabetic acidosis may be precipitated by acute appendicitis or intestinal obstruction - If abdominal pain does not promptly resolve with correction of metabolic abnormalities, suspect underlying organic problem Black Widow Spider Bites: - Produce intense pain and rigidity of abdominal muscles AND back (back involvement infrequently occurs in intraabdominal disease) Clinical Pearl: Whenever the cause of abdominal pain is obscure, a metabolic origin always must be considered.

4. IMMUNOCOMPROMISED PATIENTS¶

Evaluating and diagnosing causes of abdominal pain in immunosuppressed or otherwise immunocompromised patients is very difficult. Normal physiologic responses may be absent or masked.

4.1 High-Risk Populations¶

Organ transplant recipients
Patients receiving immunosuppressive treatments for autoimmune diseases
Patients receiving chemotherapy
Patients on glucocorticoids
Patients with AIDS
Very elderly patients

4.2 Unusual Pathogens to Consider¶

Etiologic agents include: - Cytomegalovirus - Mycobacteria - Protozoa - Fungi These pathogens may affect ALL gastrointestinal organs including: - Gallbladder - Liver - Pancreas - Gastrointestinal tract (causing occult or overtly symptomatic perforations)

4.3 Specific Conditions¶

Splenic Abscesses: - Consider Candida or Salmonella infection - Especially when evaluating patients with left upper quadrant or left flank pain Acalculous Cholecystitis: - May be observed in immunocompromised patients or those with AIDS - Often associated with cryptosporidiosis or cytomegalovirus infection Neutropenic Enterocolitis (Typhlitis): - Often identified as cause of abdominal pain and fever - Occurs in patients with bone marrow suppression due to chemotherapy - Consider acute graft-versus-host disease in this circumstance Optimal management requires meticulous follow-up including serial examinations to assess need for surgical intervention (e.g., for perforation).

5. NEUROGENIC CAUSES¶

Diseases that injure sensory nerves may cause causalgic pain with characteristic features distinct from other abdominal pain etiologies.

5.1 Causalgic Pain¶

Characteristics: - Burning character - Usually limited to distribution of a given peripheral nerve - Stimuli that are normally not painful (touch, temperature change) may be causalgic - Often present even at rest - Demonstration of irregularly spaced cutaneous 'pain spots' may be only indication of old nerve injury Distinguishing features: - Even though pain may be precipitated by gentle palpation, rigidity of abdominal muscles is absent - Respirations usually not disturbed - Abdominal distention uncommon - No relationship to food intake

5.2 Spinal Nerve/Root Pain¶

Characteristics: - Comes and goes suddenly - Lancinating type Causes: - Herpes zoster - Impingement by arthritis - Tumors - Herniated nucleus pulposus - Diabetes - Syphilis Distinguishing features: - Not associated with food intake, abdominal distention, or changes in respiration - Severe muscle spasms may be relieved by (not accentuated by) abdominal palpation - Made worse by movement of spine - Usually confined to a few dermatomes - Hyperesthesia is very common

5.3 Functional Causes¶

Irritable Bowel Syndrome (IBS): - Functional gastrointestinal disorder characterized by abdominal pain and altered bowel habits - Diagnosis based on clinical criteria (see Chapter 338) and exclusion of demonstrable structural abnormalities - Pain conforms to none of the aforementioned patterns Characteristics: - Episodes may be brought on by stress - Pain varies considerably in type and location - Nausea and vomiting are rare - Localized tenderness and muscle spasm are inconsistent or absent Pathophysiology: - Causes not yet fully understood - Proinflammatory cells and lipotoxic lipids likely play a role

6. DIFFERENTIAL DIAGNOSIS¶

The location of pain assists in narrowing the differential diagnosis. However, the chronological sequence of events in the patient's history is often more important than pain location.

Differential Diagnoses of Abdominal Pain by Usual Location¶

Location	Differential Diagnoses
Right Upper Quadrant	Cholecystitis; Cholangitis; Pancreatitis; Pneumonia/empyema; Pleurisy/pleurodynia; Subdiaphragmatic abscess; Hepatitis; Budd-Chiari syndrome

Location	Differential Diagnoses
Epigastric	Peptic ulcer disease; Gastritis; GERD; Pancreatitis; Myocardial infarction; Pericarditis; Ruptured aortic aneurysm; Esophagitis
Left Upper Quadrant	Splenic infarct; Splenic rupture; Splenic abscess; Gastritis; Gastric ulcer; Pancreatitis; Subdiaphragmatic abscess
Right Lower Quadrant	Appendicitis; Salpingitis; Inguinal hernia; Ectopic pregnancy; Nephrolithiasis; Inflammatory bowel disease; Mesenteric lymphadenitis; Typhlitis
Periumbilical	Early appendicitis; Gastroenteritis; Bowel obstruction; Ruptured aortic aneurysm
Left Lower Quadrant	Diverticulitis; Salpingitis; Inguinal hernia; Ectopic pregnancy; Nephrolithiasis; Irritable bowel syndrome; Inflammatory bowel disease
Diffuse Nonlocalized	Gastroenteritis; Mesenteric ischemia; Bowel obstruction; Irritable bowel syndrome; Peritonitis; Diabetes; Malaria; Familial Mediterranean fever; Metabolic diseases; Psychiatric disease

7. APPROACH TO THE PATIENT WITH ABDOMINAL PAIN¶

Few abdominal conditions require such urgent operative intervention that an orderly approach needs to be abandoned, no matter how ill the patient is.

7.1 Immediate Surgical Indications¶

Only patients with exsanguinating intraabdominal hemorrhage (e.g., ruptured aneurysm) must be rushed to the operating room immediately. In such instances, only a few minutes are required to assess the critical nature of the problem. Management priorities: - Sweep aside all obstacles - Obtain adequate venous access for fluid replacement - Begin operation immediately There are NO absolute contraindications to operation when massive intraabdominal hemorrhage is present. CAUTION: Many patients may die in the radiology department or emergency room while awaiting unnecessary examinations. NOTE: This does not necessarily apply to patients with intraluminal gastrointestinal hemorrhage, who can often be managed by other means (see Chapter 51).

7.2 History Taking¶

Obtaining a detailed history when possible can be extremely helpful even though laborious and time-consuming. Decision-making regarding next steps is facilitated and a reasonably accurate diagnosis can be made before further diagnostic testing. Important considerations: - In acute abdominal pain, diagnosis can be readily established in most instances - Success is less frequent in patients with chronic pain - IBS is one of the most common causes of abdominal pain (see Chapter 338) - Chronological sequence of events often more important than pain location - Careful attention to extraabdominal regions is essential Analgesia: Narcotics or analgesics should NOT be withheld until a definitive diagnosis or plan has been formulated. Obfuscation of the diagnosis by adequate analgesia is unlikely. Female Patients: - An accurate menstrual history is essential - Normal anatomic relationships can be significantly altered by gravid uterus - Abdominal and pelvic pain may occur during pregnancy due to non-operative conditions - Some otherwise noteworthy laboratory values (e.g., leukocytosis) may represent normal physiologic changes of pregnancy

7.3 Physical Examination¶

Simple critical inspection provides valuable clues: - Facies - Position in bed - Respiratory activity The amount of information gleaned is directly proportional to the gentleness and thoroughness of the examiner. Critical Points: - Once a patient with peritoneal inflammation has been examined brusquely, accurate assessment by the next examiner becomes almost impossible - Forceful demonstration of rebound tenderness is cruel and unnecessary Better Techniques for Detecting Rebound Tenderness: 1. Gentle percussion of the abdomen (rebound tenderness on miniature scale) - more precise and localizing 2. Asking patient to cough - elicits true rebound tenderness without placing hand on abdomen Note: Forceful demonstration will startle and induce protective spasm in nervous/worried patients where true rebound tenderness is not present. A palpable gallbladder will be missed if palpation is so aggressive that voluntary spasm becomes superimposed on involuntary rigidity. Timing: Sufficient time should be spent in the examination. Abdominal signs may be minimal but, if accompanied by consistent symptoms, may be exceptionally meaningful. Pelvic and Rectal Examinations: Mandatory in every patient with abdominal pain because: - Abdominal signs may be virtually or totally absent in pelvic peritonitis - Tenderness on pelvic/rectal examination in absence of other abdominal signs can indicate operative conditions such as perforated appendicitis, diverticulitis, or twisted ovarian cyst

7.4 Auscultation¶

Auscultation of the abdomen is one of the LEAST revealing aspects of the physical examination of a patient with abdominal pain. Key points: - Catastrophes (strangulating small-intestinal obstruction, perforated appendicitis) may occur with NORMAL peristaltic sounds - When proximal intestine above obstruction becomes markedly distended and edematous, peristaltic sounds may lose borborygmi characteristics and become weak or absent even without peritonitis - Usually only severe chemical peritonitis of sudden onset is associated with the truly silent abdomen

7.5 Laboratory Examinations¶

Laboratory examinations may be valuable in assessing patients with abdominal pain, yet, with few exceptions, they rarely establish a diagnosis. Leukocytosis: - Should NEVER be the single deciding factor for operation - WBC >20,000/ µ L may be observed with: - Perforation of a viscus - Pancreatitis - Acute cholecystitis - Pelvic inflammatory disease - Intestinal infarction - A normal white blood cell count is NOT rare in cases requiring surgery

8. KEY POINTS & CLINICAL PEARLS¶

Summary of critical teaching points for clinical practice.

8.1 Diagnostic Pearls¶

Catastrophic events may present with subtle symptoms - pain severity does not correlate with disease severity
'Acute or surgical abdomen' is an unacceptable diagnosis due to misleading connotations
The presence or absence of 'hunger' is unreliable as sole indicator of intraabdominal disease severity
Chronological sequence of events is often more important than pain location
Always consider intrathoracic disease in patients with upper abdominal pain
'Pain out of proportion to physical findings' is characteristic of mesenteric ischemia
Whenever cause of abdominal pain is obscure, always consider metabolic origin
Abdominal auscultation is one of the least revealing examination aspects

8.2 Examination Principles¶

Information gleaned is directly proportional to gentleness and thoroughness
Brusque examination of peritonitis patients makes subsequent accurate assessment almost impossible
Use gentle percussion rather than forceful rebound testing
Asking patient to cough detects rebound without touching abdomen
Pelvic and rectal examinations are mandatory in every patient
Sufficient time must be spent - minimal signs with consistent symptoms can be meaningful

8.3 Management Principles¶

Only exsanguinating intraabdominal hemorrhage requires abandoning orderly approach
No absolute contraindications to operation in massive intraabdominal hemorrhage
Do NOT delay analgesics until definitive diagnosis - obfuscation is unlikely
Leukocytosis should never be the sole deciding factor for operation
In immunocompromised patients, serial examinations are essential to assess need for surgical intervention
If metabolic abnormality correction does not resolve pain promptly, suspect underlying organic problem

8.4 Special Populations¶

Pregnancy: - Normal anatomic relationships altered by gravid uterus - Some lab abnormalities (leukocytosis) may be normal physiologic changes Immunocompromised: - Normal physiologic responses may be absent or masked - Consider unusual pathogens (CMV, mycobacteria, protozoa, fungi) - Meticulous follow-up with serial examinations essential Obtunded/Debilitated/Psychotic Patients: - Catastrophic emergencies may present with minimal or no detectable pain or muscle spasm