Pyogenic liver abscess overview

# Overview
Pyogeinic liver abscess is caused by the local inflammatory reaction caused by bacteria in hepatic parenchyma leading to the development of intrahepatic pus collection.They account for 80% of liver abscesses in developed world.

# Historical Perspective
Hippocrates described pyogenic liver abscess based on the type of fluid recovered from abscess. In 1938, Ocshner and colleagues reported that the major causal factors leading to hepatic abscess were appendicitis and amoebiasis.

# Classification
Pyogenic liver abscess may be classified according to international classification of diseases-10 (ICD-10) into K75.0..

# Pathophysiology
Development of pyogenic liver abscess is the result of infection through the following routes like portal vein (also from pylephlebitis of portal vein), hepatic arteries as metastatic abscesses, direct spread from nearby infection, trauma and retroperitoneal extension from appendix.Ascending biliary infection is the most common source of pyogenic liver abscess.

# Causes
Common causes of pyogenic liver abscess include hepatobiliary, portal, arterial, traumatic and cryptogenic causes.

# Differential Diagnosis
Pyogenic liver abscess must be differentiated from other diseases with similar presentation such as amoebic liver abscess, fungal liver abscess, echinococcal (hydatid) cyst and malignancy (hepatocelluar carcinoma or metastasis).

# Risk Factors
Common risk factors in the development of pyogenic liver abscess are immunodeficiency, diabetes mellitus, pancreatic or hepatobiliary disease and liver transplant.

# Screening
According to the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for pyogenic liver abscess.

# Natural History, Complications and Prognosis
If left untreated, pyogenic liver abscess may progress to peritonitis or pleuritis secondary to rupture of the abscess into peritoneal or pleural cavities and sepsis.Complications of pyogenic liver abscess include septicemia, intraabdominal abscess, hepatic failure, renal failure, recurrent liver abscess and free peritonitis.The prognosis of liver abscess depends on underlying risk factors such as advanced age, malignancy, jaundice, multiple abscesses, heamoglobin <10g/dl and elevated blood urea nitrogen.

# Diagnosis

## History and Symptoms
Symptoms of pyogenic liver abscess include abdominal pain, right lower chest pain, fever, chills, night sweats, nausea, vomiting, loss of appetite, right shoulder pain, weight loss, diarrhea, dyspnea and yellowish discoloration of skin (jaundice).

## Physical Examination
Common physical examination findings associated with pyogenic liver abscess include high grade fever, yellowish discoloration of skin (jaundice), icteric sclera, reduced breath sounds or crepitations at the base of lung, hepatomegaly with point tenderness, and abdominal guarding or rebound tenderness on palpation, dullness on percussion, and absent bowel sounds.

## Laboratory Findings
Laboratory tests consistent with diagnosis of pyogenic liver abscess include complete blood picture, ESR, C-reactive protein, liver function tests, pus culture, and blood culture.

## ECG
There are no ECG findings associated with pyogenic liver abscess.

## Chest X Ray
Chest X ray findings include atelectasis, pulmonary infiltrates, pleural effusion, elevated right hemidiaphragm, and gas within the abscess or biliary tree or beneath the diaphragm.

## CT Scan
CT scan findings of pyogenic liver abscess include peripherally enhancing and centrally hypo attenuating lesions, solid or gas in the lesions (gas in the form of bubbles or air fluid levels), segmental, wedge-shaped or circumferential perfusion abnormalities, early enhancement may be seen on contrast enhanced CT scans, the double target sign and cluster sign.

## MRI
MRI findings of pyogenic liver abscess include hypointense and heterogenous centrally on T1, hyperintense signal on T2, enhancement of the capsule and multiple septations on T1+C, high signal within the abscess cavity on DWI, and low signal within the abscess on ACD.

## Ultrasound
The ultrasound findings include round or oval shape, hypoechoic appearance with fine and homogeneous echoes, gas bubbles within the abscess, and absence of central perfusion on color doppler.

## Other Imaging Studies
Other diagnostic studies include radionucleide scans which use technetium, indium, or gallium. They detect lesions <2 cm in size. These scans cannot distinguish between the cyst, tumor, or abscess and need confirmation with other diagnostic tests.

# Treatment

## Medical Therapy
Treatment of pyogenic liver abscess include non-surgical treatment and open surgical drainage. Non-surgical treatment treatment includes conservative management with antibiotics alone and percutaneous drainage.

## Surgical Therapy
The maninstay of treatment of pyogenic liver abscess is percutaneous darinage of abscess. Other methods used are open surgical drainage and endoscopic retrograde cholangiopancreatography(ERCP).

## Primary Prevention
The risk of developing pyogenic liver abscess can be reduced by prompt treatment of abdominal and other infections.

## Secondary Prevention
Secondary prevention strategies following pyogenic liver abscess include long term monitoring which helps in preventing the complications and recurrence , monitoring the abscess cavity weekly for adequate drainage using CT or USG, persistent fever more than 2 weeks of therapy is an indication for more aggressive drainage, prolonged antibiotic therapy after discharge of patient is recommended and presence of underlying liver disease is the predisposing factor for the recurrence of pyogenic liver disease.