Acute abdomen refers to abdominal conditions characterized primarily by acute abdominal pain, requiring early diagnosis and prompt management. It is distinguished by its acute onset, variable presentation, rapid progression, and severe nature. Delayed diagnosis or improper management may pose life-threatening risks to patients.
Etiology
Acute abdomen may result from diseases affecting abdominal organs and vessels, while certain non-abdominal conditions, such as acute coronary syndrome or diabetic ketoacidosis, can also lead to severe abdominal pain. Early recognition of such conditions is crucial.
Diseases of Hollow Organs
Perforation
Examples include perforation of gastrointestinal ulcers, tumors, or diverticula.
Obstruction
Examples include intestinal obstruction, biliary obstruction, or urinary tract obstruction caused by benign or malignant conditions.
Inflammation
Examples include acute appendicitis or acute cholecystitis.
Diseases of Solid Organs
Rupture and Bleeding
Conditions such as rupture of liver tumors or traumatic rupture of the liver and spleen are common.
Inflammation
Examples include acute pancreatitis or hepatic abscess.
Vascular Diseases
Conditions include abdominal aortic dissection or ruptured aneurysms.
Vascular embolism or thrombosis affecting abdominal organs may be present.
Clinical Diagnosis and Analysis
Proper timing and selection of methods are critical for the diagnosis of acute abdomen. Advances in diagnostic techniques and methods have greatly contributed to the localization and characterization of acute abdomen, but detailed history-taking, meticulous physical examination, and logical reasoning and analysis remain indispensable.
Medical History
Present Illness History
Abdominal Pain
Based on the mechanism of pain generation, abdominal pain is categorized into visceral pain, somatic pain, and referred pain. Visceral nerves primarily transmit the sensations of stretching, distension, inflammation, or ischemia from organs, leading to visceral pain, which is usually diffuse, poorly localized, and imprecise. By embryonic origin, visceral pain from foregut, midgut, or hindgut organs is typically localized to the epigastrium, periumbilical region, and lower abdomen, respectively. Somatic nerves transmit pain originating from the abdominal wall or the parietal peritoneum, which is usually sharp, well-localized, and precise. Pain referred from abdominal pathologies may project onto the abdominal surface, perineum, back, shoulders, or other regions.
Triggers
Acute abdomen is often related to dietary factors. Gallbladder colic or acute cholecystitis commonly occurs after fatty meals, while acute pancreatitis is often associated with a history of excessive alcohol consumption or overeating. Perforation of gastric or duodenal ulcers is frequently observed after large meals, and volvulus often occurs following vigorous physical activity.
Location
The initial and most severe location of somatic pain often corresponds to the site of the lesion. For example, perforation of an acute gastric or duodenal ulcer produces pain that originates at the perforation site and quickly spreads to the entire abdomen, though the perforation site remains the most prominent area of pain.
Migration of abdominal pain is characteristic of certain conditions such as acute appendicitis. Pain typically starts in the periumbilical or epigastric region before localizing to the right lower abdomen as the appendix serosa becomes involved in the inflammatory process. Perforation of a duodenal ulcer, resulting in leakage of its contents along the right paracolic gutter, may occasionally present with similar migratory pain and warrants careful differential diagnosis.
In cases of gallbladder colic or acute cholecystitis, pain originating in the epigastrium or right upper quadrant may radiate to the right shoulder or the area beneath the right scapula. Acute pancreatitis or perforation of the posterior wall of the duodenum may be associated with back pain. Renal colic caused by an upper ureteral stone may radiate to the ipsilateral lower abdomen or groin, while stones in the lower ureter may be associated with perineal radiating pain.
Conditions outside the abdomen, such as right-sided pneumonia or pleuritis, may irritate intercostal and lumbar nerves (particularly T6-L1), resulting in right upper or lower quadrant pain, which may be misdiagnosed as acute cholecystitis or acute appendicitis.
Onset and Urgency of Pain
Perforation of hollow organs typically presents with a sudden onset of severe pain, as seen in gastric or duodenal ulcer perforations that cause immediate, intense abdominal pain. Infectious conditions, such as acute cholecystitis or acute appendicitis, tend to present more gradually, with pain worsening as inflammation progresses.
Nature of Pain
Constant dull or vague pain is often indicative of inflammation or bleeding, as observed in pancreatitis or liver rupture. Pain caused by hollow organ obstruction, such as small bowel obstruction or ureteral stones, is often characterized by paroxysmal colicky pain at onset, with an absence of pain during the intervals. Persistent pain with episodes of exacerbation is more commonly associated with conditions involving both inflammation and obstruction, or with strangulated hollow organs, such as mesenteric arterial embolism. In elderly patients, mesenteric ischemia may initially cause severe pain without obvious signs of peritonitis, with pain subsiding once bowel necrosis develops. The resultant "discrepancy between symptoms and signs" can mislead clinical judgment and result in severe consequences, necessitating heightened vigilance.
Severity of Pain
Pain arising in the early stages of inflammation is usually mild, often presenting as vague and poorly localized, but it intensifies and becomes more localized as inflammation progresses. Pain caused by perforation of hollow organs is typically severe and associated with pronounced peritoneal irritation signs. Pain resulting from visceral rupture and bleeding is less intense compared to the chemical irritation caused by gastrointestinal perforation, leading to relatively milder abdominal pain and signs.
Gastrointestinal Symptoms
Anorexia
Patients with acute appendicitis, particularly children, often exhibit anorexia before the onset of abdominal pain.
Nausea and Vomiting
Nausea and vomiting commonly follow the onset of abdominal pain. Reflex vomiting typically occurs early and almost immediately after the onset of pain, while vomiting caused by gastrointestinal obstruction tends to occur later due to the accumulation of contents. The higher the location of the pathological lesion causing abdominal pain, the earlier and more frequent vomiting tends to occur, such as in cases of acute gastroenteritis, pyloric obstruction, or high intestinal obstruction. Lesions located lower in the gastrointestinal tract tend to present later with vomiting or may not involve vomiting at all. Observations of the color, quantity, and odor of the vomit are often useful for differential diagnosis. Vomit containing undigested food and lacking bile is commonly seen in pyloric obstruction. Vomit containing bile suggests obstruction below the opening of the duodenal papilla. Vomit resembling coffee grounds suggests gastrointestinal bleeding, while fecal-like vomit typically indicates complete lower intestinal obstruction.
Defecation
The absence of bowel movements, constipation, or diarrhea following the onset of abdominal pain should be noted, as well as the characteristics of the stool. Ceasing stool passage and flatus often suggests mechanical intestinal obstruction. Diarrhea is commonly seen in diseases like gastroenteritis and also occurs in pelvic abscesses or appendicitis. Blood in the stool is frequently observed in cases such as intestinal strangulation, intussusception, or acute necrotizing hemorrhagic enteritis.
Associated Symptoms
Inflammatory conditions are often accompanied by varying degrees of fever as the disease progresses. Acute obstructive suppurative cholangitis is frequently associated with chills, high fever, and jaundice. Diseases of the urinary tract are often accompanied by symptoms such as frequent urination, urgent urination, painful urination, hematuria, or difficulty urinating. In surgical cases of acute abdomen, abdominal pain often precedes fever, while fever preceding abdominal pain is more commonly associated with medical conditions.
Menstrual History
The timing of the last menstrual period in women of childbearing age aids in assessing the likelihood of ectopic pregnancy. Rupture of ovarian follicles or corpus luteum typically occurs between two menstrual cycles.
Past History
A history of peptic ulcers accompanied by sudden onset of epigastric pain raises the possibility of ulcer perforation. A history of gallstones, combined with abdominal pain and jaundice, suggests possible migration of stones into the common bile duct. A history of abdominal surgery and paroxysmal abdominal pain may indicate adhesive intestinal obstruction. The increasing prevalence of laparoscopic gastrointestinal surgeries has resulted in a higher incidence of conditions like internal hernias or volvulus leading to intestinal strangulation, which warrants differentiation. Suspected cases of intestinal obstruction in acute abdomen always require exclusion of external hernias.
Physical Examination
General Condition and Posture
The appearance, mental state, and posture of the patient provide clues about the severity of the condition. Patients with intra-abdominal bleeding often exhibit pallor and anemic facies, while those with peritonitis often appear distressed and adopt a flexed posture to avoid stretching. Dehydrated patients may present with sunken eyes, wrinkled skin, and reduced skin elasticity. Obstruction of the biliary tract is typically associated with scleral and skin jaundice.
Abdominal Examination
The entire region from the nipples to the inguinal area should be exposed for examination. The assessment involves inspection, palpation, percussion, and auscultation, performed in sequence. Related organ systems, such as the heart and lungs, should also be examined.
Inspection
Attention should be paid to abdominal shape, skin color and elasticity, superficial veins on the abdominal wall, and other abnormal findings. For instance, abdominal distension and prominent superficial veins on the abdominal wall may appear in cases of intestinal obstruction. Scaphoid abdomen can be observed after perforation of peptic ulcers. Localized bulging or visible bowel outlines may indicate volvulus. Protrusion of a lump in the inguinal region raises suspicion of an incarcerated hernia.
Palpation
During abdominal palpation, patients are typically positioned supine with knees bent to relax abdominal muscles. Palpation begins in areas without abdominal pain or where pain is mild. Rebound tenderness, guarding, and rigidity are characteristic signs of peritonitis. The area of most pronounced tenderness often corresponds to the site of the lesion. For example, during the early stages of acute appendicitis, patients may complain of periumbilical pain, but tenderness in the right lower abdomen is already present.
Muscle guarding reflects the severity of intra-abdominal inflammation. Mild guarding is seen in cases of mild inflammation or bleeding within the abdominal cavity, while pronounced guarding suggests severe infections or suppurative inflammation, such as suppurative appendicitis or suppurative cholecystitis. Extreme guarding resembling a "board-like abdomen" is commonly seen in gastric and duodenal ulcer perforation.
It is important to note that elderly, weak patients, children, obese individuals, postpartum women, and those with severe infections or shock may exhibit abdominal signs that appear less severe than the actual disease.
Palpation should also assess for hepatosplenomegaly, abdominal masses, and the characteristics of these masses, such as shape, size, texture, and pulsation. Ruptured hepatic tumors often present as palpable masses in the right upper quadrant. Examination of male patients should include assessment of the testes for abnormalities, such as testicular torsion.
Percussion
Percussion usually begins in areas without pain or with mild pain. The region demonstrating pronounced tenderness often corresponds to the site of the lesion. Important findings in abdominal percussion involve tonal quality and boundaries. Solid organs or tumors typically produce dull sounds, while tympanic sounds indicate the presence of gas or intestinal loops beneath the region. Shifting dullness suggests the presence of ascites or intra-abdominal bleeding. Disappearance of the hepatic dullness boundary is indicative of gastrointestinal perforation.
Auscultation
Auscultation commonly starts around the periumbilical area or in the right lower abdomen. Hyperactive bowel sounds reflect increased intestinal motility. Early-stage mechanical intestinal obstruction is often characterized by increased bowel sounds, high-pitched tones, and frequently accompanied by gurgling sounds akin to "gas and liquid passing." In contrast, paralytic ileus, acute peritonitis, or hypokalemia typically result in reduced or absent bowel sounds.
Digital Rectal Examination
This examination focuses on determining the presence of rectal masses, assessing the rectal wall, the recto-uterine pouch, and cervical tenderness. Care must be taken not to confuse a woman’s cervix for a pathological mass. Observations regarding stool on the glove, including the presence of blood or mucus, contribute to diagnostic evaluation.
Auxiliary Examinations
Laboratory Tests
White blood cell count and differential are valuable in assessing the presence and severity of infection. Sequential measurements of red blood cell count, hemoglobin levels, and hematocrit help determine whether bleeding has occurred and the rate of hemorrhage. Elevated urinary white blood cell counts are indicative of urinary tract infections, while increased urinary red blood cell counts suggest the presence of urinary tract stones. Positive urinary bilirubin levels indicate obstructive jaundice. Significant elevations in blood, urine, or peritoneal fluid amylase support the diagnosis of pancreatitis. Microscopic examination of peritoneal fluid smears assists in distinguishing secondary peritonitis from primary peritonitis. Measurements of human chorionic gonadotropin (HCG) aid in diagnosing ectopic pregnancy. Procalcitonin (PCT) testing helps evaluate the progression and prognosis of acute abdominal conditions and severe surgical infections, such as peritonitis, sepsis, systemic inflammatory response syndrome (SIRS), or multiple organ dysfunction syndrome (MODS).
Imaging Studies
Ultrasound
Ultrasound is effective in diagnosing the rupture of solid organs, tumors, and stones. It also assists in the localization and quantification of ascites or intra-abdominal bleeding, and facilitates guided puncture drainage procedures.
X-Ray Imaging or Fluoroscopy
Chest and abdominal X-rays or fluoroscopy remain widely used diagnostic methods. X-ray can assess the level of the diaphragm and the presence of subdiaphragmatic free gas. Upright abdominal radiographs provide information about fluid-air levels in the intestine and bowel loop distribution, while supine radiographs show the extent of intestinal dilation, aiding in the diagnosis of intestinal obstruction. Additionally, abdominal X-rays can indicate the presence of urinary tract stones.
CT and/or MRI
CT and MRI have become routine diagnostic tools for acute abdomen cases. They reveal the location, nature, extent of lesions, and their relationships with surrounding organs. In cases of acute pancreatitis, CT scans can display the degree of pancreas swelling, ductal dilation, the presence of pancreatic ductal stones, and pancreatic exudates.
Selective Arteriography
Selective arteriography aids in the early diagnosis and treatment planning for abdominal arterial embolic diseases. It can occasionally be used to localize and treat bleeding in cases of abdominal trauma.
Duodenoscopic Examination
In cases of acute cholangitis, duodenoscopy facilitates placement of nasobiliary drainage tubes or stents at the duodenal papilla for biliary decompression, which is a commonly used therapeutic method for this condition.
Diagnostic Abdominal Puncture
Abdominal puncture may be employed when the diagnosis of abdominal pain is unclear. The puncture site is generally chosen in the outer third of the line connecting the left or right anterior superior iliac spine and the umbilicus. For female patients, puncture through the posterior vaginal fornix is also an option. Non-coagulated blood aspirated during puncture indicates intra-abdominal bleeding, while the aspiration of purulent fluid supports the diagnosis of peritonitis.
Laparoscopy
Emergency laparoscopy is recommended for patients with atypical signs of peritonitis where both diagnosis and treatment prove challenging. Laparoscopy provides diagnostic clarity and allows for timely and necessary therapeutic intervention.
Diagnosis and Differential Diagnosis
Acute Perforation of Gastric or Duodenal Ulcer
Abrupt onset of severe abdominal pain, "board-like abdomen," and free gas under the diaphragm are classic manifestations of peptic ulcer perforation. A history of peptic ulcer, sudden epigastric knife-like pain rapidly spreading throughout the abdomen, significant signs of peritoneal irritation, a "board-like abdomen," disappearance of hepatic dullness, and free gas under the diaphragm on X-ray collectively confirm the diagnosis. Some patients may not have a prior history of ulcer disease.
Acute Cholecystitis
Epigastric pain triggered by fatty food intake radiating to the right scapular region is indicative of acute cholecystitis. Physical examination typically reveals tenderness, rebound pain, and muscle tension in the right upper abdomen, with positive Murphy's sign and tenderness on percussion over the liver area. Biliary colic caused by gallstones often emerges at night and is frequently misdiagnosed as "stomach issues." Ultrasound examination showing gallbladder wall thickening, edema, and gallstones helps establish the diagnosis while ruling out common bile duct stones or obstruction.
Acute Cholangitis
Epigastric pain accompanied by chills, high fever, and jaundice are typical features of acute cholangitis. Due to the connection of intrahepatic bile ducts to hepatic sinusoids, elevated biliary pressure in cholangitis can facilitate the entry of bacteria and toxins into the bloodstream, causing septicemia and infectious shock. Typical clinical manifestations, combined with routine laboratory tests and ultrasound imaging, often confirm the diagnosis.
Acute Pancreatitis
Often associated with heavy drinking or overeating, acute pancreatitis typically presents with severe, persistent pain primarily in the left upper abdomen, radiating to the lower back. Nausea and vomiting that do not alleviate the pain are common. Elevated blood and urinary amylase levels assist in confirming the diagnosis, while abdominal CT can provide detailed confirmation.
Acute Appendicitis
Classic symptoms include migratory pain to the right lower abdomen and localized tenderness in the right lower quadrant. Pain often begins around the periumbilical or epigastric region and subsequently localizes to the right lower abdomen as inflammation involves the appendiceal serosa. Signs of localized peritonitis may appear in cases of suppurative or gangrenous appendicitis. Appendiceal perforation often leads to generalized peritonitis, but tenderness remains most pronounced in the right lower quadrant.
Acute Small Bowel Obstruction
Abdominal pain, distension, cessation of bowel movements and flatus, and vomiting are its classic clinical features. Symptoms vary according to the site of obstruction: high small bowel obstruction primarily causes vomiting with minimal distension, whereas lower small bowel obstruction prominently features abdominal distension with delayed vomiting. Early in the disease, bowel sounds are hyperactive with increased gurgling sounds. Paralytic ileus or intestinal strangulation during later stages results in diminished or absent bowel sounds. X-ray imaging is instrumental in confirming the diagnosis. Ultrasound is often diagnostic in small bowel obstruction caused by intussusception but is less useful for other types of obstruction.
Closed Abdominal Trauma
Key differentiation includes assessing for solid organ rupture with bleeding, hollow organ rupture with perforation, and vascular injury. Large-volume bleeding caused by solid organ rupture or vascular damage often presents with tachycardia and hypotension, though peritoneal irritation signs may not be prominent. Hollow organ rupture typically exhibits pronounced signs of peritonitis. Isolated abdominal wall contusions or mild solid organ injuries generally lack such severe manifestations.
Gynecological Causes of Acute Abdominal Pain
Acute Pelvic Inflammatory Disease (PID)
Common in young women, it presents with lower abdominal pain, tenderness, rebound tenderness, and possible fever. The tenderness is usually medial and inferior to the site of the appendix. Increased vaginal discharge, cervical tenderness on digital rectal examination, and purulent fluid on posterior fornix puncture with Gram-negative diplococci in white cells confirm the diagnosis.
Ovarian Tumor Torsion
Torsion of ovarian cysts is the most common cause. Patients typically have a history of ovarian cysts and experience a sudden onset of pain. Signs of peritonitis suggest tumor ischemia and necrosis due to torsion.
Ectopic Pregnancy
The most common cause is rupture of a tubal pregnancy. A history of amenorrhea and sudden onset of lower abdominal pain with signs of peritonitis indicate potential ectopic pregnancy. Signs of hemorrhage, such as tachycardia and hypotension, suggest massive intra-abdominal bleeding. While abdominal tenderness and muscle guarding may be mild, rebound tenderness is usually evident. Non-clotting blood collected during abdominal or posterior fornix puncture supports the diagnosis. Positive HCG and pelvic ultrasound findings are also diagnostic.
Management Principles
The underlying cause must be identified promptly, and appropriate measures must be implemented. For cases where the diagnosis remains unclear, admission for observation, fasting, intravenous fluid replacement, and close monitoring are required while further diagnostic measures are undertaken.
The use of potent analgesics like morphine should be avoided if the diagnosis is uncertain, as they may mask disease progression and delay diagnosis.
Surgical exploration or treatment requires appropriate preoperative preparation based on the patient’s condition.
Emergency surgical exploration is generally indicated in cases of unclear diagnosis with any of the following conditions:
- Vascular compromise, such as intestinal necrosis;
- Infection that cannot be localized or shows signs of spreading;
- Active intra-abdominal bleeding;
- Deterioration or lack of improvement despite non-surgical treatment in the absence of systemic medical conditions, especially in cases involving hemodynamic instability or organ dysfunction.
The primary surgical principle is to prioritize life-saving measures, followed by disease resolution. Surgical approaches should be simple and effective when possible. For critically ill patients, damage control principles should be observed, initially addressing life-threatening issues, with definitive surgery performed once the patient's condition stabilizes. Emergency laparoscopic surgery is increasingly utilized for acute abdominal conditions and offers advantages such as minimal invasiveness and quicker recovery. It is particularly beneficial for the diagnosis and treatment of complex or challenging cases.