illnesshacker: Medical information and health advice you can trust.

Acute Abdomen – Causes, Symptoms, Diagnosis, Treatment

Acute Abdomen is a condition that demands urgent attention and treatment. The acute abdomen may be caused by an infection, inflammation, vascular occlusion, or obstruction. The patient will usually present with sudden onset of abdominal pain with associated nausea or vomiting. Most patients with acute abdomen appear ill.

Acute abdomen is occasionally used synonymously with peritonitis. While this is not entirely incorrect, peritonitis is the more specific term, referring to inflammation of the peritoneum. It manifests on physical examination as rebound tenderness or pain upon removal of pressure more than on the application of pressure to the abdomen. Peritonitis may result from several of the above diseases, notably appendicitis and pancreatitis. While rebound tenderness is commonly associated with peritonitis, the most specific finding is rigidity.

The approach to a patient with an acute abdomen should include a thorough history and physical exam. The location of the pain is critical as it may signal a localized process. However, in patients with free air, it may present with diffuse abdominal pain. Auscultation may reveal absent bowel sounds and palpation may reveal rebound tenderness and guard, suggestive of peritonitis. The causes of an acute abdomen include appendicitis, perforated peptic ulcer, acute pancreatitis, ruptured sigmoid diverticulum, ovarian torsion, volvulus, ruptured aortic aneurysm, lacerated spleen or liver, and ischemic bowel.[rx][rx][rx]

Pathophysiology

The pathophysiology of each disease entity is beyond the scope of this review. Causes include infection (appendicitis, diverticulitis) and obstruction (appendicitis, cholecystitis). Anatomic abnormalities include malrotation of the gut. Age is associated with some diseases: older patients are more likely to present with diverticulitis, cholecystitis, and vascular emergencies.

The classic presentations of appendicitis, cholecystitis, pancreatitis, and diverticulitis, are in large part the result of the dual innervation of the abdomen, both visceral and somatic. Visceral nerves are part of the autonomic nervous system and innervate the viscera. These nerves are sensitive to mechanical distention, inflammation, ischemia, and the intense, smooth muscle contraction seen in colic. The pain is often midline, poorly localized, deep, and dull. Pain from embryonic foregut structures such as the stomach, liver, pancreas, and gallbladder radiate to the epigastrium. Midgut structures, small bowel, and appendix, to the periumbilical area and hindgut, large bowel and rectum, to the lower abdomen. Somatic sensory nerves provide sensation to the parietal peritoneum. Somatic pain is sharper and better localized. Somatic pain suggests peritoneal irritation. An example is a pain over McBurney’s point when the inflamed or ruptured appendix is irritating the parietal peritoneum. Because visceral and somatic afferent nerve fibers share spinal cord segments, visceral pain can be felt as referred pain from a somatic distribution. This explains cholecystitis radiating to the right scapula.

Types of Acute Abdomen

Ischemic acute abdomen

Vascular disorders are more likely to affect the small bowel than the large bowel. Arterial supply to the intestines is provided by the superior and inferior mesenteric arteries (SMA and IMA respectively), both of which are direct branches of the aorta.

The superior mesenteric artery supplies:

Small bowel
Ascending and proximal two-thirds of the transverse colon

The inferior mesenteric artery supplies:

Distal one-third of the transverse colon
Descending colon
Sigmoid colon

Of note, the splenic flexure, or the junction between the transverse and descending colon, is supplied by the most distal portions of both the inferior mesenteric artery and superior mesenteric artery, and is thus referred to medically as a watershed area, or an area especially vulnerable to ischemia during periods of systemic hypoperfusion, such as in shock.

The acute abdomen of the ischemic variety is usually due to:

Thromboembolism from the left side of the heart, such as may be generated during atrial fibrillation, occluding the SMA.
Nonocclusive ischemia, such as that seen in hypotension secondary to heart failure, may also contribute, but usually results in a mucosal or mural infarct, as contrasted with the typically transmural infarct seen in thromboembolic of the SMA.
Primary mesenteric vein thromboses may also cause ischemic acute abdomen, usually precipitated by hypercoagulable states such as polycythemia vera.

You Might Also Like Acid-Base Disorders - Causes, Symptoms, Diagnosis, Treatment

Bleeding

The most serious cause of intra-abdominal bleeding – is a ruptured abdominal aortic aneurysm, which requires swift referral to the vascular team and immediate surgical intervention.
Other common causes – usually involve a slower rate of bleeding, but with urgent surgery still required, include ruptured ectopic pregnancy, bleeding gastric ulcer, and trauma.
These patients will typically go into hypovolemic shock. Clinical features include tachycardia and hypotension, pale and clammy on inspection, and cool to touch with a thread pulse.

Perforated Viscus

Peritonitis – is the inflammation of the peritoneum, and a generalised peritonitis is most commonly caused by perforation of an abdominal viscus.
The causes of perforation are broad but include peptic ulceration, small or large bowel obstruction, diverticular disease, and inflammatory bowel disease.

Patients with generalised peritonitis present with some characteristic features:

Patients often lay completely still, not to move their abdomen, and look unwell
- This is especially important when compared to renal colic, whereby patients are constantly moving and cannot get comfortable.
Tachycardia and potential hypotension
A completely rigid abdomen with percussion tenderness
Involuntary guarding – the patient involuntarily tenses their abdominal muscles when you palpate the abdomen
Reduced or absent bowel sounds, suggesting the presence of a paralytic ileus

Causes of Acute Abdomen

Common causes of an acute abdomen include acute appendicitis, cholecystitis, pancreatitis, and diverticulitis. Acute peritonitis is a cause of acute abdomen and can result from rupture of a hollow viscus or as a complication of inflammatory bowel disease or malignancy. Vascular events causing an acute abdomen include mesenteric ischemia and ruptured abdominal aortic aneurysm. Obstetric and gynecologic causes include ruptured ectopic pregnancy and ovarian torsion. Urologic conditions including ureteral colic and pyelonephritis can also present as acute abdominal pain. Many authors include small bowel obstruction as a cause of acute abdomen. Newborns can present with necrotizing enterocolitis. Midgut volvulus present 40% of the time in the first week of life, 50% in the first month and 75% in the first year. Intussusception usually occurs at ages nine to 24 months. The most common cause of an acute pediatric abdomen is appendicitis.[rx]

The differential diagnoses of acute abdomen include:

Acute appendicitis
Acute peptic ulcer and its complications
Acute cholecystitis
Acute pancreatitis
Acute intestinal ischemia (see section below)
Acute diverticulitis
Ectopic pregnancy with tubal rupture
Ovarian torsion
Acute peritonitis (including hollow viscus perforation)
Acute ureteric colic
Bowel volvulus
Bowel obstruction
Acute pyelonephritis
Adrenal crisis
Biliary colic
Abdominal aortic aneurysm
Familial Mediterranean fever
Hemoperitoneum
Ruptured spleen
Kidney stone
Sickle cell anaemia
Carcinoid

Having abdominal surgery is a risk factor of this condition. Causes can be divided into six large categories, including inflammatory, mechanical, neoplastic, vascular, congenital, and traumatic.

Inflammatory

Irritation of the inner abdominal cavity or its lining (the peritoneum) can trigger inflammation leading to acute abdomen. Irritation and inflammatory acute abdomen can be triggered by:

Bacterial infections – Such as those that result in diverticulitis or appendicitis.
Peptic ulcers – If ruptures occur, peptic ulcers releases gastric acid that can irritate the perineum.

Mechanical

Mechanical causes include any action to the abdominal contents that can cause obstructions within the abdomen, such as:

Twisting
Malrotation
Herniation

Neoplastic

Neoplastic refers to benign or malignant cancerous processes. Acute abdomen can occur when a tumor or mass within the abdomen presses upon organs or cause obstructions.

Vascular

Acute abdomen may occur if the abdomen’s blood supply is affected, such as by blockage from narrow arteries or by clots within the vessel.

Congenital

Defects in the abdominal structure that are present at birth can result in inflammation or blood vessel problems that cause obstructions.

Traumatic

Direct damage to the abdomen in the form of trauma can cause acute abdomen, including:

Gunshot wounds
Stabbing
Mechanical vehicle accidents
Blunt abdominal injuries

Symptoms of Acute Abdomen

Main symptom

Severe abdominal pain is the main symptom of acute abdomen. However, it can be accompanied by a host of other symptoms.

You Might Also Like Achlorhydria - Causes, Symptoms, Diagnosis, Treatment

Other symptoms

Further symptoms of acute abdomen include:

Fever
Constipation
Bloody stool
Rebound tenderness – When the abdomen is pressed deeply, more pain is felt upon removal of the pressure rather than the application of the pressure.
Rigidity – The abdomen feels very hard and stiff and worsens when touched.
Guarding – Reactive stiffening/hardening of the abdomen in response to pressure or touch is an involuntary reflex to prevent pain caused by any pressure on the abdomen.
Abdominal distention/stomach bloating
Jaundice – Yellowing of the skin or whites of the eyes results from excessive breakdown of red blood cells or obstruction of the bile duct near the liver.
Colic – Sharp, localized pain in the abdomen increases to a peak then subsides.
Migratory pain – Pain that begins above the belly button and migrates to the right lower quadrant of the abdomen is specific to certain conditions that can be very helpful in diagnosis.

Diagnosis of Acute Abdomen

History and Physical

The history and physical exam serve to eliminate some diagnoses and suggest others. Acute care physicians are well aware of the modes of presentation of these disease entities. The immediate onset of pain suggests a vascular event such as mesenteric ischemia. Syncope hints at blood loss as from a ruptured ectopic or leaking abdominal aortic aneurysm (AAA). Various causes of an acute abdomen have classic presentations. Appendicitis is supposed to start with dull periumbilical pain that migrates with time to the right lower quadrant. Ovarian torsion is supposed to start with sudden, unilateral, lower abdominal pain that waxes and wanes and is associated with vomiting. Unfortunately, most diseases fail to present classically. A leaking abdominal aortic aneurysm can present exactly like renal colic or as apparently a benign low back pain. The clinician simply has to consider serious diagnoses in patients at risk.

Pain in various quadrants suggests varying diagnoses. Acute diverticulitis usually lives in the left lower quadrant while cholecystitis is usually felt in the epigastrium or right upper quadrant. Diagnosing a patient with a full-blown acute abdomen is easy. It is amazingly difficult to diagnose an incipient abdominal catastrophe in a patient presenting with early, non-specific symptoms.

The past medical history can be important. Hypertension is a risk factor for abdominal aortic aneurysm. The social history regarding alcohol use and possible pancreatitis, helps as well.

The physical exam should be focused and completed in a timely fashion. Abnormal vital signs or the general appearance of the patient including facial expression, skin color and temperature, and altered mentation should alert the clinician that a patient may be in extremis. A complete abdominal exam is essential. Bowel sounds must be assessed. Palpation for masses, pain, guarding and rebound is important. Classic teaching demands a rectal on every patient with abdominal pain. Literature suggests that rectal exam, at least in appendicitis, does not add any useful information. Certainly, a rectal exam is important when gastrointestinal (GI) bleeding or prostate issues are suspected. A pelvic exam should be performed when a gynecologic source of pain is suspected. A young male with abdominal pain needs a testicular exam to exclude testicular torsion. Examination for hernias should be routine.

Evaluation

ECG – Diagnostic interventions include blood work and imaging. In adults older than 40, a 12 lead ECG can help exclude myocardial infarction as the cause of apparent severe abdominal pain. It is important to know if a patient with mesenteric ischemia is in atrial fibrillation.
Complete blood count (CBC) – comprehensive metabolic profile and lipase are obtained. For sepsis or mesenteric ischemia, lactate should be ordered.
A urine or serum pregnancy test – is needed in the workup of ectopic pregnancy. Diagnostic imaging has advanced rapidly in the past three decades.
A bedside ultrasound – in the Emergency Department can diagnose cholecystitis, hydronephrosis, hemoperitoneum, and the presence of an abdominal aortic aneurysm in less than 5 minutes. Diagnostic ultrasound is the preferred modality for cholecystitis, pediatric appendicitis, ruptured ectopic, and ovarian torsion.
Multislice helical CT scanning – has made the diagnosis of an acute abdomen much more straightforward. In the majority of cases, intravenous (IV) contrast is sufficient. Oral contrast is time-consuming and not usually necessary. MRI is not usually utilized simply because of the time required in a potentially unstable patient.[rx][rx][rx]

Ultrasound:
- Kidneys, ureters and bladder (‘KUB’) – for suspected renal tract pathology
- Biliary tree and liver – for suspected gallstone disease
- Ovaries, fallopian tubes and uterus – for suspected tubo-ovarian pathology
Radiological:
- An erect chest X-ray (eCXR) – for evidence of bowel perforation (Fig. 3)
- CT imaging, often best discussed with a senior depending on the suspected underlying diagnosis

You Might Also Like FASDs; Causes, Symptoms, Diagnosis, Treatment

Laboratory Tests

The investigations in all cases of the acute abdomen share the same generic outline:

Urine dipstick – for signs of infection or haematuria ±MC&S. Include a pregnancy test for all women of reproductive age.
ABG – useful in bleeding or septic patients, especially for the pH, pO₂, pCO₂, and lactate for signs of tissue hypoperfusion, as well as a rapid haemoglobin.
Routine bloods – FBC, U&Es, Liver Function, CRP, amylase.
- Consider measuring serum calcium in suspected pancreatitis.
- Do not forget a group & save (G&S) if the patient is likely to need surgery soon.

Blood cultures – if considering infection as a potential diagnosis

Note: Any amylase 3x greater than the upper limit is diagnostic of pancreatitis. Any raised value lower than this may also be due to another pathology, such as perforated bowel, ectopic pregnancy, or diabetic ketoacidosis (DKA)

Treatment of Acute Abdomen

Hypotension and tachycardia suggest blood loss, hypovolemia, or sepsis and require prompt aggressive fluid resuscitation with adequate large bore IV access. Broad-spectrum antibiotics covering gram-negative enteric organisms should be administered in a timely fashion when infection, peritoneal spoilage, or sepsis is in the differential. Sick patients should be monitored with ongoing vital sign resuscitation. Adequate pain relief with opioids is a standard of care. The use of anti-emetics is likewise important. If a surgical emergency is suspected based on a presentation or physical findings, a surgeon should be consulted in an emergent fashion. The surgeon must be contacted before potentially time-consuming testing is performed.

In summary, the acute abdomen consists of several intrabdominal processes that require rapid intervention in both diagnosis and treatment. An acute abdomen may present in an obvious or subtle manner, but must always be recognized. Rapid, appropriate testing and concomitant resuscitative therapy are mandatory. If the condition is even possibly surgical, early consultation with a surgeon is mandatory as well.

Complications

If left untreated, an acute abdomen may result in the following:

Sepsis
Necrosis and/or gangrene of bowel
Fistula
Death

Postoperative and Rehabilitation Care

Since most patients with an acute abdomen are seniors, they are best managed in an ICU setting. Intravenous hydration, Nasogastric decompression and pain control are often required. The role of antibiotics depends on the cause. Close monitoring is required as patients may develop complications like atelectasis, ileus, wound infections, DVT and pneumonia.

References

If the article is helpful, please Click to Star Icon and Rate This Post!

[Total: 0 Average: 0]

Acute Abdomen – Causes, Symptoms, Diagnosis, Treatment

Acute Abdomen – Causes, Symptoms, Diagnosis, Treatment

Pathophysiology