HistoryA 5-week-old female Labrador Retriever was evaluated because of lethargy and abdominal distention. The owner reported feeding the puppy with her littermates a few hours prior to evaluation. The puppy had a normal to ravenous appetite and was active at that time. The puppy had no prior history of illness and was the same size as its littermates. On physical examination, the puppy was quiet and had signs of depression. Mucous membranes were pale and the puppy had tachycardia (180 to 200 beats/min) with moderate femoral pulses. Abdominal distention was apparent with gas tympany. Abdominal radiographs were obtained (Fig 1). Determine whether additional imaging studies are required, or make your diagnosis from Figure 1-then turn the page * *