Repeat ultrasound was performed 3 days later:
The right kidney was unremarkable and seems completely resolved. The left kidney now measures 11.76 cm. The free fluid appears to have resolved. The caudal half of the kidney is completely destroyed and likely no longer viable.

Contrast iodine study could be considered. Some pericapsular inflammation was noted. Even if some residual function is noted in the cranial half of the left kidney I strongly recommend a nephrectomy. Color flow assessment of the cranial half of the kidney appeared to be adequate. Heminephrectomy could be considered at the time of surgery, yet there is still a potential of this being a neoplastic process such as hemangiosarcoma. Therefore, surgical exploratory is recommended with likely expectation of left nephrectomy or heminephrectomy if not neoplastic and still viable from a surgical perspective. There was a slight blood clot noted between the vena cava and aorta, yet this appears to be resolving. Therefore, that portion is likely not neoplastic. However, there is still a potential of intrarenal neoplasia, though less likely given that the abdominal presentation appears to be largely resolved and localized around the left kidney. Alternatively, if the patient is stable continuation of supportive therapy could be considered with a recheck of the kidney in approximately 1 week to assess for further potential resolution. If the patient is not stable and still painful then a left nephrectomy would be recommended.