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Dx: Mild Hydronephrosis
Image 1 shows the left kidney with mild hydronephrosis.
The renal parenchyma, outlined with asterisks, is echoic (dark gray), the renal pelvis is hyperechoic (white) and the dilated collecting system demonstrates mild hydronephrosis anechoic (black). No kidney stone is seen. Image 2 shows a cross section of her normal aorta, with the IVC and vertebral body labeled. Her aortic diameter is under 2cm. Time permitting, it is generally quite helpful to practice imaging other parts of the body. The ultrasound machine is already there and set up and the more you practice looking at normal anatomy, the better you will become at detecting abnormal findings.
Remember that it’s always a good idea to get a comparison view of structures that are bilateral. A view of a normal right kidney will help to ensure that the hydronephrosis on the painful side is indeed unilateral. If you see bilateral hydronephrosis with unilateral flank pain, you might need to expand your differential diagnosis a bit. Does your patient have distal obstruction? Are there two disease processes occurring simultaneously? Does that patient have an abscess, mass, or infarct that can’t be visualized well on bedside ultrasound?
As for the final question, “Do you need a formal study?” the answer is, “it depends.” How confident are you in your diagnosis and what was your pre-test probability? Are there red cells in the UA? Is the patient willing to wait or pay for additional testing? How backed up is the waiting room? Does your hospital or group have a policy covering this? Who is the patient going to follow-up with, and are they likely to applaud or complain about you? I can’t answer these questions for you, but I would be quite satisfied with myself if I saved her a CT scan.
Continue to next page for Pearls and Pitfalls for Renal Ultrasound