The incidence of viral hepatitis is rising globally as well in Pakistan. Seasonal rains and floods that occur during the Monsoon season take advantage of poor sanitary conditions in third world countries like Pakistan and result in epidemics of fecal-orally transmitted diseases such as viral hepatitis. 
Definite diagnosis of AVH requires serological analysis for antibodies but these serological tests are expensive and practically out of reach for the plenteous poor of the developing world. On the other hand, the technique of ultrasonography is easily available and hence clinical diagnosis of hepatitis made upon classical features like jaundice, pale stools, right hypochondriac pain may be supplemented by ultrasound findings. To this purpose, many studies have evaluated and emphasized the importance of ultrasonographic findings of AVH.
A case-control study done in a tertiary care hospital of India by Maurya et al. included patients of all ages. They found out that hepatomegaly (86.6%) and GWT (75.8%) were the most significant ultrasound findings in AVH.
GWT is one of the most important features of AVH. There are multiple causes of GWT that are suggested in the literature. This sonographic feature may be non-specific alone but is highly sensitive for the diagnosis of acute hepatitis. In the context of vomiting and fever, GWT remains the most important feature of acute hepatitis. [9, 10]
The exact pathophysiology of GWT in acute hepatitis can be explained by three possible mechanisms. First, there is hepatocyte injury leading to decreased bile production. This results in decreased gallbladder volume and a relative increase in gallbladder wall thickness. Secondly, there is direct inflammation of layers of the gallbladder wall caused by the virus contained in bile with resultant edema of the gallbladder wall. The third explanation is that hepatocyte necrosis causes inflammation to be spread to the gallbladder resulting in GWT. 
In our study, GWT was present in 82.9% of the patients and pericholecystic edema in 65.9% of the patients. In a study conducted by Sudhamshu KC, 84% of the patients showed GWT. In a similar study by Sudhamshu et al, GWT was seen in 91% of the patients. Important AVH findings of pericholecystic edema and gall bladder sludge were seen in 65% and 48% of the patients respectively. Both these studies show a frequency of GWT almost identical to ours. A recent study of AVH patients by Maurya et al. conducted in 2019, showed GWT in 75.8% of the cases, further signifying this finding. [7, 11, 12]
The prognostic value of gallbladder wall thickness was specifically assessed by Ahn et al. in Korea. It showed direct relation to gallbladder wall thickness and liver enzyme elevation. They divided the patients into two groups, Group A included patients having increased gallbladder wall thickness and Group B with normal gallbladder wall thickness. Patients were studied in terms of ultrasonographic features, liver enzymes, hospital stay duration, and follow up ultrasound. They concluded that liver enzyme elevation and duration of hospital stay were significantly associated with increased gallbladder wall thickness. 
Another important imaging parameter in AVH is bright periportal triads giving a ‘starry sky appearance’. In our study, it was seen in 63.8% of the patients. This typical appearance of the periportal triads is due to edema of liver cells that decreases the echogenicity of the liver. The edema further causes an alteration in sound properties and accentuates the walls of portal venous channels. 
In a study done by Shin et al, 71–75% of the patients revealed starry sky appearance whereas GWT was found in 77–100% of the patients of severe acute hepatitis. They concluded that both starry sky appearance and gallbladder wall thickness is important in predicting severe acute hepatitis A. 
Hepatomegaly is also an important finding in ultrasonography of hepatitis patients. It was present in 28 (59.5%) of our patients. Girish N et al. found hepatomegaly in 37 of their cases (76%).  Hepatomegaly was found to have an occurrence of 30% in a study by Modi et al. 
Our study revealed a very predictably low pattern of vaccination in the diseased Pakistani population (Table: Supplemental File 1). Only 72.3% of the patient has received vaccination. This shows that lack of vaccination trend is another cause of the occurrence of epidemics of AVH year after year in Pakistan, despite claims of mass vaccination campaigns by the government.