Musculoskeletal Back Pain with Renal Impairment and Hepatic Enzyme Elevation Due to Medication: This could be due to medications such as NSAIDs that are known to cause both renal impairment and hepatic enzyme elevation, and are commonly used for back pain. The negative renal ultrasounds reduce the likelihood of obstructive causes, making this a plausible explanation for her symptoms.

Pyelonephritis or Kidney Infection: Despite negative ultrasounds, an infection could cause both renal dysfunction and back pain. The absence of obstructive findings on ultrasound does not rule out an infectious process.
Nephrolithiasis (Kidney Stones): Although the ultrasounds were negative, small stones might not be visible. The right-sided lower back pain could be indicative of a stone, especially if it's causing an obstruction not yet visible on ultrasound.
Hepatorenal Syndrome: This condition involves renal dysfunction in the setting of advanced liver disease. The elevated liver enzymes could suggest liver disease, which in turn could lead to hepatorenal syndrome.

Abdominal Aortic Aneurysm (AAA): Although less common in females, an AAA could cause back pain and, if ruptured, could lead to renal impairment due to hypovolemia or direct compression/involvement of the renal arteries. This is a medical emergency.
Renal Cell Carcinoma: A tumor could cause both pain and renal dysfunction. The negative ultrasound does not entirely rule out a small or isoechoic tumor.
Obstructive Uropathy Due to Malignancy: Similar to renal cell carcinoma, other malignancies could obstruct the urinary tract, leading to renal impairment. The absence of findings on ultrasound does not exclude this possibility, especially if the obstruction is more proximal (e.g., at the ureteropelvic junction) or due to external compression.

Amyloidosis: This condition can cause both renal impairment and liver enzyme elevation, though it is less common. It could also potentially cause back pain if there is spinal involvement.
Sarcoidosis: A systemic disease that can affect both the kidneys and liver, causing dysfunction and enzyme elevation. Back pain could be due to vertebral involvement.
Primary Biliary Cholangitis (PBC) or Other Autoimmune Hepatitis: These conditions could explain the liver enzyme elevation and, in rare cases, might be associated with renal dysfunction and back pain due to systemic inflammation or associated conditions like Sjögren's syndrome.