Hot quadrate sign

Hot Quadrate Sign refers to a radiological sign observed in nuclear medicine, particularly in hepatobiliary scintigraphy. This sign is indicative of cholecystitis, an inflammation of the gallbladder, and is considered a specific finding for this condition. The hot quadrate sign is characterized by increased radiotracer uptake in the liver's quadrate lobe (segment IV) relative to the rest of the liver. This increased uptake is due to the collateral circulation that develops in response to the obstructed cystic duct in acute cholecystitis.

Background

Hepatobiliary scintigraphy, also known as a HIDA scan, is a diagnostic procedure used to evaluate the function of the liver, gallbladder, and bile ducts. A radioactive tracer is injected into the patient, which the liver processes and excretes into the bile. In a healthy individual, the tracer flows smoothly from the liver into the gallbladder and bile ducts. However, in conditions like cholecystitis, the flow is disrupted, leading to specific patterns on the scan.

Clinical Significance

The hot quadrate sign is significant because it helps in the differential diagnosis of acute cholecystitis. It is particularly useful in cases where the diagnosis is uncertain after initial clinical evaluation and ultrasound findings. The presence of the hot quadrate sign on a HIDA scan supports the diagnosis of acute cholecystitis, guiding further management and treatment decisions.

Pathophysiology

The pathophysiology behind the hot quadrate sign involves the development of collateral circulation as a compensatory mechanism in response to the obstructed cystic duct. This obstruction leads to increased pressure and inflammation in the gallbladder, prompting the formation of new blood vessels that reroute the blood flow. These new vessels supply the quadrate lobe of the liver, resulting in increased radiotracer uptake in this area compared to the rest of the liver.

Diagnosis

The diagnosis of acute cholecystitis with the help of the hot quadrate sign involves performing a HIDA scan. The patient is injected with a radiotracer, and images are taken over time to observe the tracer's flow. A positive hot quadrate sign is indicated by the visualization of increased tracer uptake in the liver's quadrate lobe. This finding, combined with clinical symptoms and other diagnostic tests, can confirm the diagnosis of acute cholecystitis.

Treatment

The treatment for acute cholecystitis typically involves antibiotics to control the infection and surgery to remove the gallbladder (cholecystectomy). The identification of the hot quadrate sign can expedite the decision-making process for surgical intervention, thereby reducing the risk of complications associated with untreated cholecystitis.

Conclusion

The hot quadrate sign is a valuable diagnostic tool in the evaluation of suspected acute cholecystitis. Its presence on a hepatobiliary scintigraphy scan provides specific evidence of this condition, aiding in accurate diagnosis and timely management.