Uncommon Causes of Acute Abdominal Pain

Introduction:

Acute abdominal pain is usually the most sought-after gastroenterological problem. The pain may be severe and intense, affecting an area or a large part of the abdomen, depending on the underlying cause. Abdominal pain may be acute (remains for a short duration) or chronic (remains for a long time of nearly three months). Recurrent abdominal pain occurs intermittently, and it is also of a longer duration. The underlying cause for the abdominal pain needs to be evaluated promptly considering various investigations and needs to be ruled out to avoid misinterpretations that might impact the treatment outcomes.

What Is Acute Abdominal Pain?

Acute abdominal pain refers to the sudden onset of severe abdominal pain which might be due to gastrointestinal issues like nausea, vomiting, or indigestion and sometimes might be more serious due to infection, inflammation, obstruction, or vascular occlusion requiring immediate medical care.

What Are the Uncommon Causes of Acute Abdominal Pain?

Digestive problems are one of the most common causes of abdominal pain. It is assumed that abdominal pain is usually a stomach ache, but the abdomen region consists of important organs, muscles, blood vessels, and connective tissues that include the stomach, kidneys, liver, small and large intestines, appendix, pancreas, gallbladder, spleen and also houses inferior vena cava and the core abdominal muscles which keep the trunk stable.

As many vital organs are placed in the abdominal region, the causes for acute abdominal pain may be diverse and varied and need to be ruled out carefully. Some of the uncommon causes of acute abdominal pain include,

Chronic Abdominal Wall Pain:

• Chronic abdominal wall pain (CAWP) is also called anterior cutaneous nerve entrapment syndrome.

• CAWP occurs commonly but is often misdiagnosed, and ten to 30 percent of the patients present with simple abdominal pain.

• Diagnosis is often misled in such cases and interpreted promptly only after extensive investigations.

• Women are more prone to have CAWP than men, the ratio being 4:1.

• CAWP is also more common in co-morbid, obese, and patients with depression.

Pathophysiology:

• When the cutaneous branches of the thoracic nerves are trapped in the rectus abdominis muscle, it may end up causing abdominal wall pain.

Clinical Features:

• Pain is usually localized and occurs in the right upper quadrant of the stomach, which is the most common site.

• Allodynia (a type of nerve pain that occurs even due to non-painful stimuli such as light touch).

• Hyperalgesia (a condition in which a person suffers increased sensitivity to pain).

• Pain worsens with activities such as bending, sitting, lying on the affected side, coughing, and sneezing, which tense the abdominal muscles.

Diagnosis:

• Physical examination is the most important diagnostic rule in the case of CAWP.

• Positive Carnett’s sign (patient’s abdominal muscles are tensed and cause tenderness when the patient tries to touch his chest with the chin, raising both the legs) and positive pinch test (when the affected side is pinched, leading to increased tenderness and pain when compared to the contralateral side) gives a clue to the diagnosis.

Management:

• The treatment of CAWP comprises reassurance, modifying activity, and pain management using topical analgesics, neuromodulators, and TPI (trigger point injection).

• Rigorous movements that tense the abdominal muscles in the affected site, which aggravate the pain, should be avoided.

• Patients with mild pain can benefit from the topical application of the Lidocaine patch.

• Some patients prefer having heat pads and ice packs to be placed on the affected site to relieve the pain.

• TPI (trigger point injections) can be given to patients suffering from moderate to severe pain. Ultrasound guidance may or may not be taken to inject Lidocaine with or without Betamethasone or Triamcinolone at the site of maximum pain.

• If the pain persists even after multiple TPIs, other possible causes of chronic pain should be ruled out.

• If the pain does not regress or resolve even after meticulous treatment with multiple TPIs in the case of CAWP, chemical neurolysis and surgical interventions should be considered.

Vascular Causes of Recurrent Abdominal Pain:

Vascular disorders which cause persistent or chronic abdominal pain are

Median Arcuate Ligament Syndrome (MALS):

• Median arcuate ligament syndrome (MALS) is a chronic postprandial abdomen pain caused due to occlusion of the celiac artery by the median arcuate ligament of the diaphragm.

• It is also known as celiac artery compression syndrome.

• Middle-aged women are more prone to MALS, especially those who are thin.

Pathophysiology: MALS occurs due to ischemia of the celiac artery due to diaphragmatic compression, thus causing severe pain.

Clinical Features:

• Postprandial epigastric pain.

• Weight loss.

• Nausea.

• Vomiting.

• Diarrhea.

• Intensified abdominal bruit on deep expiration.

Diagnosis:

• Computed tomography-assisted angiography (CTA) or a magnetic resonance angiogram (MRA) is advised, and the patient is filmed during deep expiration.

• Localized narrowing of the celiac arteries is seen when the diaphragm descends more than the artery, giving the clue to the diagnosis.

• Duplex ultrasound with inspiratory and expiratory measurements is also of great importance in the diagnosis.

Management:

• Open and laparoscopic surgery is indicated for symptomatic patients confirmed with MALS.

• Also, CT (computed tomography) or endoscopic ultrasound–guided celiac ganglion blockade with local anesthetic agents or ethanol can be initiated.

Chronic Mesenteric Ischemia (CMI):

• Chronic mesenteric ischemia (CMI) is a rare entity constituting less than

five percent of all ischemic disorders of the intestine and is mostly of atherosclerotic origin.

• Most commonly occur in women.

Pathophysiology:

• CMI is also referred to as intestinal angina.

• Occurs due to reduced intestinal blood flow because of mesenteric atherosclerosis or vasculitis, leading to clinical manifestations, which are aggravated by increased metabolic demands.

Clinical Features:

• Postprandial abdominal pain.

• Weight loss.

• Nausea and vomiting.

• Diarrhea.

• Lower gastrointestinal bleeding.

Diagnosis:

• Clinical features and radiologic imaging are most commonly employed to diagnose CMI.

• Imaging studies are done using CT angiography, which is more specific and sensitive.

• Duplex ultrasonography has also been used.

• High-grade stenosis greater or equal to 70 percent occlusion in two or more of the major mesenteric vessels gives the diagnosis.

• Functional testing methods, such as visible light spectroscopy and gastric tonometry exercise testing, have been employed for more accurate diagnosis.

• Postprandial serum D-dimer and lactate levels are also used, as they are elevated in patients with CMI.

Management:

• Surgical or endovascular revascularization is the treatment of choice for CMI to relieve the symptoms and is considered a priority in young patients with long life expectancies.

Subacute Mesenteric Venous Thrombosis (SMVT):

• Subacute mesenteric venous thrombosis (SMVT) usually presents as recurrent abdominal pain of a longer duration without intestinal infarction.

• Most commonly affects the elderly.

Pathophysiology:

• SMVT occurs as a result of hypercoagulability, stagnant blood flow, and endothelial damage affecting the duodenum, jejunum, or ileum.

• SMVT usually occurs due to venous occlusion, resulting in ischemia.

• The portal, superior mesenteric, and splenic veins are most commonly affected.

Clinical Features:

• This is characterized by the “tumbleweed” pain pattern, which occurs as a relapsing, remitting nature of pain.

Diagnosis:

• Physical examination and lab tests are beneficial in diagnosing SMVT.

• Radiologic studies such as CTA and magnetic resonance venography (MRV) are used as they are more specific and accurate.

• Occlusion of the mesenteric veins, compensated by collateral circulation, is pathognomic of SMVT.

Management:

• A conservative approach is employed by administering systemic anticoagulants for three to six months, preventing thrombus growth and to encourage recanalization.

• Surgical intervention is indicated for patients with bowel infarction.

Conclusion:

Timely diagnosis and effective management of recurrent abdominal pain are vital in providing appropriate care to such patients. The misinterpretations and wrong diagnoses not only lead to unnecessary hospitalizations, surgeries, and testing but also end up in disease progression and can have a negative impact on the overall treatment outcomes. Hence, gastroenterologists should have adequate knowledge regarding the rare and common causes of abdominal pain, and the condition should be managed effectively.