Introduction

Diagnosis is of acalculous cholecystitis is difficult. Clinical examination is often not helpful, as many patients are receiving mechanical ventilation and have decreased mental awareness. The diagnosis is usually made by radiological tests, most often by sonographic examination of the gallbladder. The role of the various imaging modalities in acute acalculous cholecystitis is still somewhat controversial. In general, no single imaging study is ideal. The three primary imaging modalities (ultrasound, CT scan and cholescintigraphy) often are complementary. Early diagnosis and management is of vital importance as without immediate treatment the condition rapidly progresses to perforation or gangrenous cholecystitis with very high mortality. A timely diagnosis will depend on a high index of suspicion in the appropriate patient, and the combined results of clinical findings (admittedly nonspecific), plus properly interpreted imaging.

Case presentation

A 68-year-old female was presented to the emergency department at KFMC, Riyadh, with complaints of recurrent upper abdominal pain and vomiting for two months which got worse 4 days before her presentation. She had no past history of medical illness or surgery. On admission to the emergency department, she was fully conscious, oriented, not jaundiced or cyanosed. Her pulse was 93/minute, blood pressure 104/70 mm of Hg, temperature 37.6°C, respiratory rate 22/minute and oxygen saturation 98% at room air. The chest was clear and abdominal examination revealed tenderness in the right hypochondrium and epigastric region, and a positive Murphy’s sign. The rest of the abdomen was soft and not tender.

CBC showed an Hb of 10.2 g/dl, WBCs of 10.8 x10³ and platelets of 27 x10³. Urea and electrolytes and liver function test showed elevated urea, creatinine and liver enzymes with marginally elevated serum bilirubin and alkaline phospatase (table 1).

Figure 1

A CT scan of the abdomen reported an echo-free gallbladder with thickened wall, mucosal enhancement, and pericholecystic fluid. The liver showed no obvious intrahepatic bile duct dilatation or focal lesion. The findings were suggestive of acalculous cholecystitis; however, further correlation with ultrasound study of the biliary system together with the laboratory and the clinical findings was recommended by the radiologist (Figure1).

Figure 2

Figure 1: Abdominal CT scan showing mucosal enhancement of the gall bladder wall with pericholecystic fluid and fat stranding

The ultrasound showed a normal liver without focal lesions or biliary duct dilatation. The gallbladder was echo-free with a thickened wall (figures 2 and 3). There was free fluid seen in Morison’s pouch, the infrahepatic area, around the left and right kidneys (figure 4 and 5), and also in the pelvis. The ultrasound findings confirmed the CT findings of features of acalculous cholecystitis.

Figure 3

Figure 2: Ultrasonography showing an echo-free gall bladder with edematous thickened wall

Figure 4

Figure 3: Ultrasonography showing thickened gallbladder wall surrounded with pericholecystic fluid together with right perinephric fluid.

Figure 5

Figure 4: Ultrasonography showing right perinephric fluid

Figure 6

Figure 5: Ultrasonography showing fluid around the left kidney

Up to this stage the patient was only seen by the emergency physicians and junior surgical staff. Admission to the surgical ward was planned on the assumptive diagnosis of acalculous cholecystitis. Fortunately enough, the patient was seen by a clinically oriented senior surgical staff member who discovered that what was thought to be a positive Murphy’s sign was in fact enlarged tender liver and that there was obvious increase in jugular venous pressure and bilateral lower limb edema. Diagnosis of congestive heart failure was established and immediate cardiac consultation was sought. A bedside echocardiogram showed a dilated right ventricle and atrium together with a right atrial mass (thrombus) extending through the tricuspid valve into the right ventricle. Immediately after performing the echocardiogram, her oxygen saturation dropped and the patient required endotracheal intubation and ventilation. A spiral chest CT scan was ordered to rule out pulmonary embolism, but on reviewing the upper cuts of the abdominal CT scan by a senior radiologist, it was obvious that there were pulmonary emboli almost completely occluding both the right and left pulmonary arteries (figure 6).

Figure 7

Figure 6: Upper cuts of abdominal CT showing emboli almost completely occluding the right and left pulmonary arteries (arrows)

The patient was admitted to the CCU with a multidisciplinary team including cardiology, pulmonology, hematology and surgery. Retrospectively, it was very clear that the radiological findings of acalculous cholecystitis had distracted the junior staff from a more serious medical issue that was immediately endangering the patient’s life.

Discussion

Acute acalculous cholecystitis (AAC) is an acute inflammation of the gallbladder in the absence of gallstones (1). It was first described by Duncan in 1844 complicating surgery on a patient with incarcerated hernia (2). Acute acalculous cholecystitis is rare, occurring in only 5 % to 10 % of patients with acute cholecystitis (3). It is a potentially fatal form of acute cholecystitis that usually occurs in critically ill patients (4).

Acalculous cholecystitis is more likely to be found in patients with recent severe trauma, critical illness, cardiovascular surgery (5, 6, and 7) or severe burns. It has also been found in association with total parenteral nutrition (8), mechanical ventilation, and the use of narcotic analgesics, as well as in major cardiovascular disorders, complicated diabetes mellitus, autoimmune disease (9-12), AIDS (13) and after radiotherapy (14).

The precise mechanism of the disease is unknown: the commonly postulated theories regarding its pathogenesis are bile stasis, sepsis and ischemia (15, 16, and 17).

Although recognized for more than 150 years, acute acalculous cholecystitis remains an elusive diagnosis. This is likely because of the complex clinical setting in which this entity develops and lack of large prospective controlled trials that evaluate various diagnostic modalities (18).

The disease may often go unrecognized due to the complexity of the patient's medical and surgical problems. Clinical examination is often not helpful, as many patients are receiving mechanical ventilation and have decreased mental awareness. It is usually difficult to elicit right quadrant tenderness or Murphy’s sign in those patients. Biochemical markers are nonspecific and contribute to the delay in diagnosis and treatment (19). The diagnosis is usually made by radiological tests, most often by sonographic examination of the gallbladder. A timely diagnosis will depend on a high index of suspicion in the appropriate patient, and the combined results of clinical findings (admittedly nonspecific) plus properly interpreted imaging (18).

Ultrasound is usually the first line of investigation because it is widely available and can be performed at the bedside (20,21). The most significant ultrasonographic findings are thickening of the gallbladder wall of more than 3.5 mm, gallbladder distention, pericholecystic fluid, and a sonolucent intraluminal layer (22, 23). Although ultrasonography is considered as an effective and accurate diagnostic test for acalculous cholecystitis (16), the reported sensitivity and specificity of sonography in the evaluation of acalculous cholecystitis vary from 23-95% and 40-95%, respectively (24).

Computed tomography usually demonstrates the same findings of ultrasound (21, 22). The advantage to CT compared with ultrasound is that it is superior at detecting pathology elsewhere in the abdomen that could be the cause of the patient's fever or pain, but it cannot be applied at the bedside, which is necessary for many critically ill patients.

The diagnosis of acute acalculous cholecystitis with CT requires that 2 major diagnostic criteria be met or, alternatively, that 1 major criterion and 2 minor criteria be met. These criteria are as follows:

Major criteria

Minor criteria

Summary

Acute acalculous cholecystitis is a rare variety of gallbladder inflammation. It is a potentially fatal form of acute cholecystitis that usually occurs in critically ill patients. Recently acalculous cholecystitis was reported to have increasing incidence in outpatients without typical predisposing critical illness or trauma. Without immediate treatment, the condition rapidly progresses to perforation or gangrenous cholecystitis, with a mortality as high as 65%. Diagnosis of acalculous cholecystitis may depend mainly on radiological findings due to decreased patient mental awareness secondary to trauma or/and diminished patient responses due to sedation and ventilation which makes eliciting of the clinical signs difficult and sometimes impossible. The pitfalls of radiological diagnosis result in over- or under-estimation of the condition. We believe that over-diagnosis of acalculous cholecystitis is permissible and may be safer in critically ill patients and recommend maintaining a low threshold for instituting empiric, minimally invasive therapy in the form of percutaneous cholecystostomy. On the other hand, over-estimation of the condition in outpatients without typical predisposing critical illness may be dangerous as it may distract the attention of the treating physician from more serious medical issues that need urgent attention and immediate management.