Abdominal distention can be caused by various disorders in the abdomen and abdominal organs. In order to determine the nature of the disorders, diagnostic ultrasound of the uterus, urinary bladder, liver, spleen and general abdomen was conducted in 90 dogs, 36 males and 54 females, 6 months to 11 years old, with chief complaint of abdominal distention. Ultrasound examination was performed using an ultrasound machine equipped with a 3.5 MHz convex array scanner and the ultrasound features of the different organs were determined. Of the 90 dogs, abnormal ultrasound features of various organs were observed in 76 dogs while no abnormal ultrasound features were observed in 14 dogs with abdominal distention. In 24 dogs with abnormal abdominal ultrasonograms, the general abdomen contained anechoic to slightly hypoechoic areas or hyperechoic masses. In 26 dogs, the uterus contained viable gestational sacs, dead fetus or had enlarged uterus. In 10 dogs, the urinary bladder had thickened wall, hemorrhage, urolith or break in the wall. In 8 dogs, the liver appeared small or had hyperechoic parenchyma, hyperechoic masses, thickened gall bladder or enlarged hepatic veins. In 8 dogs, the spleen appeared enlarged, extending to both sides of the abdomen until the cranial border of the urinary bladder. The results suggest that diagnostic ultrasound can be an important tool for determining the causes of abdominal distention in dogs.