Critical Care Medicine

Abdominal Pain in the ICU

ABDOMINAL PAIN IN THE ICU

1. Description of the problem

Abdominal pain in the ICU patient can be a difficult complaint to investigate because the clinician must determine the extent of the discomfort and whether it portends a serious problem. ICU patients are mostly intubated and sedated and are often postoperative, so determining the significance of abdominal pain can be daunting. Non-abdominal causes can present as abdominal pain, such as cardiac (myocardial infarction), esophageal (esophagitis), or thoracic (pneumonia). Abdominal pain assessment in the ICU is often reverse of the classic approach of eliciting the history, character, and localization of the pain from the patient, then obtaining if necessary directed testing. The intensivist is left to interpret systemic signs and changes in patient's condition to determine if abdominal pain is present and possibly a harbinger of a new or worsening malady.

Key management points

The key is to recognize early signs of changing status of the patient and to assess if there is a life-threatening process present. New tachycardia, tachypnea, intolerance to tube feeds or change in bowels may give clues to underlying process. New or worsening metabolic acidosis, leukocytosis or shift, changing liver function or coagulation may add support to the diagnosis.

In summary, in most ICU patients abdominal pain if present is difficult to detect and the abdominal exam can be equivocal. This leaves a high index of suspicion in context with the known history of the patient to determine what is the likely cause of an abdominal process. For instance, in the patient with cardiogenic shock requiring pressors previously, new-onset abdominal pain/tenderness could be ischemic bowel.

2. Emergency Management

As with all patients, stabilization of airway, breathing and circulation is first and foremost. However, once these are established, workup of an acute abdominal process can be ongoing.

ICU patients can have de novo abdominal processes not associated with their admitting diagnosis. However, history of their present illness is often key to narrowing the problem, especially if the patient is unstable. Examples include:

-- Intra-abdominal hemorrhage in a trauma patient with non-operatively treated splenic injury

-- Pancreatitis in patient status post cardiac bypass

-- Sepsis from an anastomotic leak in a patient after bowel resection

-- Ischemic bowel in a patient with mitral valve endocarditis and emboli

If sepsis is suspected with an abdominal source, appropriate broad-spectrum antibiotics should be given within the first hour.

If significant pain is present, the pain should be treated and treatment should not be delayed awaiting surgical consultation. Pain management has been shown not to significantly change or delay diagnosis of the cause of abdominal pain.

3. Diagnosis

Differential diagnosis of abdominal pain in the ICU patient

Esophagitis

Pneumonia

Acute coronary syndrome

Gastritis

Gastric distention

Peptic ulcer disease

Ileus

Bowel obstruction

Ischemic/infarcted/perforated bowel

Inflammatory bowel disease

Mesenteric angina

Enteritis

Appendicitis

Diverticulitis

Colitis

Pseudo-obstruction (Ogilvie's)

Constipation

Hepatitis

Hepatic congestion

Biliary colic

Acalculous cholecystitis

Calculous cholecystitis

Ascending cholangitis

Splenic infarction

Renal calculi

Pyelonephritis

Tubo-ovarian abscess

Ectopic pregnancy

Pelvic inflammatory disease

Ruptured ovary cyst

Aortic/iliac aneurysm rupture

Abdominal aortic dissection

Pancreatitis

Typhlitis

Primary peritonitis (SBP, bile peritonitis)

Secondary peritonitis (enteric perforation)

Cystitis

Prostatitis

Urinary retention/distended bladder

Rectus sheath hematoma

Abdominal wall hernia

Necrotizing fasciitis

Cellulitis of abdominal wall

Lupus serositis

Sickle cell crisis

Establishing the diagnosis

Although anatomically not considered within the abdomen, retroperitoneal and pelvic structures will be included in this discussion.

If the patient is able to complain of pain in the abdomen, then it would be of benefit to elicit as much information from the patient as possible about the history, quality and localization of the pain.

Abdominal pain should be characterized by:

Distribution: generalized or localized; does the pain radiate?

Character: sharp, crampy, dull, constant or intermittent

Timing: did it begin acutely within minutes or develop over hours?

Location and distribution of pain can suggest the underlying structures involved. Generalized pain usually suggests structures that occupy more than one quadrant of the abdomen, such as with small bowel obstruction or colitis. Pain within one section of the abdomen can suggest an underlying etiology, such as left lower quadrant and sigmoid diverticulitis.

Information as to what relieves or exacerbates the pain can be helpful, as well as whether this is new or recurrent pain. Associated signs and symptoms such as nausea, vomiting, obstipation, fever and chills can be useful.

Temporally related events such as initiation of tube feeds, removal of urinary catheter or clamping of nasogastric tube can suggest causes such as gastric distention or urinary retention.

The majority of ICU patients are not able to give a detailed history if any at all. It then falls on the intensive care team to detect changes in the patient's condition. Therefore, at least daily a full physical exam should include a complete abdominal exam with inspection, auscultation, percussion and palpation. Changes in these aspects of the exam coupled with changes in systemic signs such as tachycardia, fever, increased minute ventilation, intolerance of tube feeds, jaundice, or oliguria should raise the suspicion of a possible abdominal process.

Inspection of the abdomen includes changes in skin, presence of ecchymoses, erythema and inspection of wounds and drains if present. Character of drainage and/or change can be important clues. Distention should be noted as well as changes in abdominal wall or groin hernias.

Although ausculation of bowel sounds is often not helpful in the ICU patient, if heard the character may suggest an underlying partial obstruction (rushes) or distention (high-pitched tingling). Bruits may suggest aneurysm. Percussion again can have some value if marked abnormalities are noted such as fluid wave, tenderness or markedly distended bowel; however, like ausculation, the usefulness in the ICU patient is limited.

Palpation is usually the most revealing part of the exam if a serious abdominal process is present. Noting guarding, tenderness and rebound are all important aspects. Identifying masses within or new asymmetry of rectus muscle can signal possible rectus sheath hematoma. However, lack of tenderness or guarding in an ICU patient may not rule out a serious abdominal problem, especially in those patients who are heavily sedated or paralyzed or on steroids.

Observation of the patient may also be helpful. If the patient is moving and writhing in pain, this can be more consistent with biliary colic, mesenteric ischemia or partial small bowel obstruction. However, patients with peritonitis generally lie still, as slight movements can cause significant abdominal pain.

Diagnostic tests and procedures

Radiographic studies such as upright chest and KUB may suggest free air or an obstructive pattern but often are nondiagnostic. Ultrasound is useful if pain is in the right upper quadrant or consistent with renal colic. However, the most useful screening tool in the ICU patient is the CT scan. It assesses the abdomen and retroperitoneal as well as pelvic structures.

Interventions such as endoscopy can be guided in certain patients to diagnose upper and lower intestinal pathology.

Early involvement of surgical consultants is important since interpretation of significant peritoneal signs can vary from one physician to another. If the surgical consultant feels that by exam and clinical suspicion surgical intervention is warranted, then delay for further testing might be harmful to the patient. An equivocal CT scan in the face of clinical peritonitis should not preclude an operative intervention.

Pathophysiology

Causes of abdominal pain in the ICU patient are many and often the exact cause is not found. Sometimes the cause is not abdominal but referred to the abdomen, such as pneumonia or hepatic congestion from right-sided heart failure. ICU patients, like other patients, will have common non-life-threatening causes of abdominal pain; however, the key is to determine if the pain, in context of the patient's current condition, is a marker of a more serious pathology.

See Flowchart. Figure 1.

Figure 1.

Abdominal Pain in the Critically Ill flowchart: The work up for abdominal pain in a critically ill patient is often simplified by approaching the pain in a step wise fashion. One method is by determining presence, degree and location of tenderness. One caveat to this is that the critically ill patient may have blunted abdominal signs secondary to pain medications, steroids, decreased mental status or other conditions. If in doubt as to the significance of abdominal pain in the critically ill patient, surgical consultation early should be considered. RLQ - Right Lower Quadrant; RUO - Right Upper Quadrant; LUQ - Left Upper Quadrant; LLQ - Left Lower Quadrant; CBC - Complete Blood Count; bHCG - beta human chorionic gonadotropin; CXR -Chest x-ray; KUB - Kidney, Ureter and Bladder x-ray (flatplate); US - Ultrasound; HIDA scan - Hepato Iminodiacetic Acid scan; EGD - esophagogastroduodenoscopy; AAA - Abdominal Aortic Aneurysm

Epidemiology

N/A

Special considerations for nursing and allied health professionals.

N/A

What's the evidence?

Silen, W. Cope's Early Diagnosis of the Acute Abdomen. Oxford University Press. 2005.

Thomas, SH, Silen, W, Cheema, F. "Effects of morphine analgesia on diagnostic accuracy in emergency department patients with abdominal pain (a prospective randomized trial).". J Am Coll Surg. vol. 196. 2003. pp. 18-31.

Dries, DJ. "Abdominal problems in the ICU: acute abdomen/pancreatitis/biliary infection and injury". ACCP Crit Care Med Brd Rev. vol. 20. 2009. pp. 301-320.

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