A patient arrives in the emergency department with severe stomach pains, vomiting and fever. The condition is serious and has to be treated quickly as life-threatening illnesses could be the cause of these symptoms. The working diagnosis is ‘acute abdomen’. Here we are going to examine what is covered by this commonly used term, which clinical diagnostics are expedient and which differential diagnosis could be considered.
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Definition of Acute Abdomen

Acute abdomen as a symptom complex

Acute abdomen is not a standalone diagnosis, but a blanket term for a symptom complex whose primary manifestation by definition is acute, extremely severe abdominal pains which constitute a threat to the life of the patient. Symptoms can have both abdominal and extra-abdominal causes.

The term acute abdomen is used to describe a patient’s condition until a final etiological explanation can be given and a diagnosis can be made, and it always describes an emergency situation. The phrase acute abdomen should therefore be carefully selected in a clinical context.

Key symptoms of acute abdomen


Image: “Pneumoperitoneum” by Clinical_Cases. License: CC BY-SA 2.5

The following complaints can be part of the acute abdomen symptom complex in a variety of forms and are considered to be key symptoms:

  • Stomach pains, acute and severe
  • Peritonitis (muscular defense)
  • Disruption of the intestinal function or peristalsis
  • Symptoms of shock (disruption of circulatory regulation)
  • Poor general health

Etiology of Acute Abdomen

Causes of acute abdomen

Note: The most important causes of acute abdomen are inflammations or perforations of the intraperitoneal organs (e.g. appendix, bile ducts and stomach); intestinal obstruction (ileus) and visceral circulatory problems.
Ulcerating and necrotizing appendicitis with perforation

Image: “Ulcerating and necrotizing appendicitis with perforation.” by Patho. License: CC BY-SA 3.0

These most common causes of acute abdomen should always be ruled out first. As acute abdomen can also have extra-abdominal causes, it makes sense to conduct a targeted observation and examination by organ system. In this manner, pains as a result of a myocardial infarction, or similarly swelling of the ovaries (adnexitis) in women, can be identified.

Symptoms of Acute Abdomen

Complaints associated with acute abdomen

The clinical symptoms of acute abdomen are as numerous as the causes, and some of those which could contribute are:

  • Acute, severe stomach pains
  • Abdominal wall tension
  • Disruption of intestinal motility, even as severe as paralysis
  • Debilitated general condition
  • Nausea and vomiting
  • Tachycardia, tachypnea
  • Difficulty in breathing
  • Fever, leukocytosis
  • Septic shock or Hypovolemic shock
  • Oliguria or anuria

Image: “Tachypnea” by Icewalker cs. License: CC BY 3.0, the image was trimmed

Atypical symptoms in older patients with acute abdomen

It is important to know that acute abdomen presents in a more diffuse manner in older patients than younger ones. Complaints are less specific and symptoms are either not present or less pronounced.  For example, gall stone pathology, such as side and back pain or nausea, are presented in only 40% of cases and even fewer, 13% of patients also develop fever and leukocytosis, where these symptoms are much more pronounced in younger patients.

Appendicitis also presents later and with similarly diffuse symptoms in older patients. The amount of complications caused by the resultant cholangitis and ruptured appendixes and the dangers of sepsis from these are far higher in older patients due to delayed diagnosis – a fact which must be considered as the attending physician.

Diagnosis of Acute Abdomen

Clinical diagnosis of acute abdomen

Acute abdomen represents an emergency situation. Several of the possible disease complexes which could lie at the heart of the diagnosis require a prompt causal therapy for the patient. Weighing up how thorough an initial diagnosis is required before proceeding with the first steps of treatment is different from case to case and depends on the following factors:

  • Hemodynamic stability of the patient: Hemodynamic instability, such as unexplained decreases in blood pressure, can be indicative of bleeding. Indications of internal bleeding would suggest treatment with immediate surgery.
  • Extent of peritonism: Local or diffuse as a measure of the progression of the symptoms.
  • Clinical stability of the patient or is their condition rapidly deteriorating?

Anamnesis for acute abdomen

A rigorous and complete anamnesis can give clues to the causes of the complaints. It is important to ask:

  • Where the pain began and the current location of it in order to gain clues to the primarily affected organ.
  • Type of pain: Description of the intensity and nature of the attendant symptoms.
    • Visceral pain: Relatively hard to pinpoint, dull, pressing pain that often radiates to other regions of the body, as well as vegetative attendant symptoms such as vomiting, sweating and hypotension e.g. stomach ulcer perforation or inflammation
    • Colic pain: Belongs to the visceral pain category, increasing and decreasing intensity, extremely unsettled patients e.g. gallstones, kidney stones or ileus.
    • Somatic pain: Relatively easy to locate, although becomes increasingly diffuse in advanced peritoneal irritation, pricking to stabbing pain, often only mild or no vegetative attendant symptoms at all e.g. appendicitis.
  • Age of patient: Probable diagnoses of certain disease complexes can be evaluated based on the age of the patient. While invagination and testicular torsion are relatively common amongst younger patients, perforations of the GI tract or tumors are more common diseases amongst adults. This knowledge also allows for more targeted clinical diagnosis.
  • Patient medication history: The medication history of the patient is very important. If surgical symptoms present, then we have to determine the use of anticoagulants such as Phenprocoumon.

Clinical investigation of the patient with acute abdomen

In order to clinically examine a patient with acute abdomen, it is necessary to:

  • Palpation of the abdomen

    Image: “Palpation of the Abdomen” by Pöllö. License: CC BY 3.0

    Inspection for injuries or hematomas, hernias, other abdominal wall defects or skin discoloration (pancreatitis).

  • Auscultation: This should always be performed prior to manual examination in order to avoid provoking intestinal noises. Intestinal sounds should be auscultated in 4 sections. Are there intestinal noises present? What grade are they? If no noises are heard, this could indicate a paralytic ileus.
  • Palpation for muscular defense, Peritonism (rebound tenderness), pain location, pain intensity, resistances and ascites.
  • Digital rectal examination for conditions such as palpable tumors, an empty bowel (caused by an obstacle such as ileus or tumor) and blood.
Note: A digital rectal examination is always employed by acute abdomen – a fact which is commonly asked in examinations!

Laboratory testing for acute abdomen

The laboratory parameters which have to be called for in addition to an emergency diagnosis are decided upon based on key factors from the patient’s medical history and clinical examination. The minimum blood requirements are:

  • Blood count (leukocytes, hemoglobin, hematocrit)
  • C-reactive protein (CRP)/Inflammatory parameters
  • Amylase or lipase in the serum (rises in pancreatitis)
  • Cholestasis parameters (rise in gallbladder inflammation)
  • Lactate (rises in mesenteric ischemia for example)
  • Electrolytes
  • Blood sugar
  • Urine sediment (leukocytes/blood on suspicion of kidney stones or ureteral calculi)

Clinical imaging diagnostics for acute abdomen

Based on the observations from the anamnesis and the clinical examination, a targeted diagnostic investigation should take place.

Sonography of the abdomen

A sonography of the abdomen is the most cost effective and fastest procedure to carry out. It can be used as a first line, orientating investigation, used principally to identify free fluids such as blood, ascites and the contents of ruptured hollow organs in the abdomen.

Injuries to the parenchymatous organs, widening or perforations of vessels (abdominal aorta, ureter or bile ducts) can also be noticed. In paralytic ileus, a sonogram often has a poor resolution due to the superimposition of air.

X-Ray of the abdomen

Abdominal X-Rays serve, for example, to identify free air in the abdomen which can occur as a result of perforation of the hollow organs. Plain radiography in a standing or left lateral position can depict this. Standing, free air is visible as a sub-diaphragmatic crescent of air, whereas lying down, an air inclusion between the liver and flank. An intestinal obstruction (ileus) can be visualized by increased fluid levels in the small and large intestines.

CT scan of the abdomen

A CT scan is the gold standard in diagnostics for acute abdomen if there is a justifiable suspicion of acute inflammation of the pancreas (pancreatitis) or if there is a diverticulum (diverticulitis). It is also of use in cases where sonography results are less meaningful e.g. in obese patients, if there is air superimposition or if there are large injuries. Advantages of a CT scan include a shorter investigation time and good picture resolution.

Differential Diagnosis

Similar pathologies to acute abdomen

Differential diagnosis of acute abdomen simultaneously differentiates the possible causes of the disease. The literature on the subject suggests different possible categories of differential diagnoses.

Categorizing by the location of pain is prudent as an initial orientation measure – which organ system could be responsible for causing pain locally or could project an effect onto the affected area? The next step is to consider which diseases of those organs identified could be responsible for the particular pattern of complaints. The most important differential diagnoses are illustrated below.


Organ System Organ with clinical picture
Upper abdomen (both sides possible) Lungs/Pleura: Pleurisy, Pneumonia, Pneumothorax, Pulmonary embolism
Heart: Acute Myocardial infarction, Pericarditis
Kidneys: Renal pelvis calculi, nephritic abscess, pyelonephritis
Right upper abdomen Bile ducts: cholecystitis, cholangitis
Pancreas: pancreatitis
Duodenum: duodenal ulcer
Liver: hepatitis, liver abscess, ruptured liver, congested liver
Epigastrium Stomach: Peptic ulcers, Gastritis
Small intestine: Ileus
Left upper abdomen Spleen: splenic infarction, ruptured spleen
Pancreas: pancreatitis, pancreatic cancer
Lower abdomen (both sides possible) Intestines: Diverticulitis
Urinary: acute urinary retention, kidney or ureter stones, testicular torsion
Gynecological.: ovarian cysts, extra uterine pregnancy, duct rupture, inflammation of the ovaries (adnexitis)
Right lower abdomen Intestines: Appendicitis
Central abdomen, Navel Intestines: Ileus (mechanical), Mesenteric ischemia, volvulus, invagination, toxic megacolon, intestinal infection, Crohn’s disease, ulcerating colitis
Left lower abdomen Intestines: sigmoid diverticulitis

Possible further methods of classification are by specialism (internal medicine, gynecology) and also anatomically or by root cause (thoracic, urogenital, vascular, traumatic, metabolic etc.). This can be an advantage in the identification of a differential diagnosis. As the most functional clinical approach for acute abdomen is classification by pain location, we have listed these classifications above.

Treatment of Acute Abdomen

Conservative or operative measures for acute abdomen

Treatment of acute abdomen is based upon the causes and is either conservative or operative depending on the diagnosis (e.g. appendectomy, cholecystectomy for appendicitis or cholecystitis). If abdominal pathology indicates a secondary peritonitis, then this has to be treated with antibiotics. It is important not to primarily prescribe cephalosporin in this case. This class of antibiotic has a loophole for enterococci and would therefore not be effective against a number of common bacteria that cause acute abdomen – a point which is commonly asked about in written medical exams.

Note: Cephalosporins are not to be used as an initial treatment for peritonitis due to their reduced effectiveness against enterococci.

Disease Progress and Prognosis of Acute Abdomen

The course and prognosis for acute abdomen are highly dependent on the causal factors as acute abdomen is only a working diagnosis until a final clarification of the symptoms can be achieved.

Review Questions

Solutions can be found below the references.

1. Which procedure is obligatory during the examination of patients with symptoms of acute abdomen?

  1. Digital rectal examination
  2. MRT scan
  3. Abdominal CT
  4. Cranial nerve status
  5. Neurological examinations using major reflexes

2. Which antibiotics should not be prescribed as the first choice when there is a suspicion of secondary peritonitis?

  1. Ampicillin
  2. Linezolid
  3. Vancomycin
  4. Mezlocillin
  5. Cephalosporin
  6. Piperacillin

3. Which of these are amongst the most common causes of acute abdomen?

  1. Appendicitis, cholecystitis, ileus, visceral circulatory disorders
  2. Appendicitis, adnexitis, cholecystitis, ileus
  3. Appendicitis, myocardial infarction, Ileus, visceral circulatory disorders
  4. Appendicitis, testicular torsion, cholecystitis, adnexitis
  5. Appendicitis, aortic aneurysm, ileus, cholecystitis


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