Photo Quiz

Acute Sharp Flank Pain


Am Fam Physician. 2021 Aug ;104(2):201-202.

A 54-year-old patient presented with stiffness and pain in the lower back and both thighs. The pain was worse when sitting and lying down, but there was no pain when standing. The patient described the pain as compression in the flanks that radiated to the right groin and both lateral thighs.

The patient had urinary hesitancy but no trauma, fever, weight loss, or blood in the urine. Symptoms were not relieved with ibuprofen and cyclobenzaprine. The medical history was significant for renal stones and gastroesophageal reflux. The patient had no history of back problems or repetitive lifting.

Physical examination revealed normal motor strength in the lower extremities and negative findings on the straight leg raise test. There was tenderness on palpation of the right flank. Results of a point-of-care urinalysis were normal. Prostate-specific antigen was mildly elevated at 5.84 ng per mL (5.84 mcg per L). Computed tomography (CT) of the abdomen was performed (Figure 1).




Based on the patient's history and physical examination findings, which one of the following is the most likely diagnosis?

  • A. Angiomyolipoma.

  • B. Metanephric adenoma.

  • C. Oncocytoma.

  • D. Renal abscess.

  • E. Renal cell carcinoma.


The answer is E: renal cell carcinoma. Renal cell carcinoma is often an incidental finding until the tumor enlarges to an advanced size. Presenting symptoms vary and include hematuria, abdominal pain, or a palpable mass. The likelihood of renal cell carcinoma is higher when all three of these symptoms are present (the classic triad). Approximately 80% to 85% of tumors in the renal cortex are renal cell carcinomas. In these cases, paraneoplastic symptoms may develop because of the production of ectopic hormones such as erythropoietin, parathyroid hormone–like protein, gonadotropins, chorionic somatomammotropin, adrenocorticotropic hormone–like substance, renin, glucagon, and insulin.1

The diagnostic workup for renal cell carcinoma includes CT or ultrasonography, although ultrasonography is less sensitive. Magnetic resonance imaging can be used in some patients. In this patient, CT identified a mass in the right kidney measuring 3.8 cm × 4.0 cm × 3.5 cm. Resection is necessary if imaging studies cannot differentiate benign renal lesions from carcinoma. Tissue biopsy of the mass can establish the diagnosis of malignancy and identify the histopathologic type. Clear cell subtypes, as in this patient, account for up to 75% of cases.2

Angiomyolipoma is a benign renal tumor that can grow to impair renal function. It is strongly associated with tuberous sclerosis, a multisystem autosomal dominant genetic disease, and lymphangioleiomyomatosis. On histology, angiomyolipomas are composed of blood vessels, smooth muscle cells, and fat cells. Patients may be asymptomatic, but rupture of involved blood vessels can result in retrop

Address correspondence to Phillip Kim, MD, MPH, at Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.


show all references

1. Gold PJ, Fefer A, Thompson JA. Paraneoplastic manifestations of renal cell carcinoma. Semin Urol Oncol. 1996;14(4):216–222....

2. Muglia VF, Prando A. Renal cell carcinoma: histological classification and correlation with imaging findings. Radiol Bras. 2015;48(3):166–174.

3. Bissler JJ, Henske EP. Renal manifestations of tuberous sclerosis complex. In: Kwiatkowski DJ, Holets Whittemore V, Thiele EA, eds. Tuberous Sclerosis Complex: Genes, Clinical Features and Therapeutics. Wiley; 2010:321–325.

4. Davis CJ Jr, Barton JH, Sesterhenn IA, et al. Metanephric adenoma. Clinicopathological study of fifty patients. Am J Surg Pathol. 1995;19(10):1101–1114.

5. Abrahams NA, Tamboli P. Oncocytic renal neoplasms: diagnostic considerations. Clin Lab Med. 2005;25(2):317–339.

6. Demertzis J, Menias CO. State of the art: imaging of renal infections. Emerg Radiol. 2007;14(1):13–22

This series is coordinated by John E. Delzell Jr., MD, MSPH, associate medical editor.

A collection of Photo Quiz published in AFP is available at

The editors of AFP welcome submissions for Photo Quiz. Guidelines for preparing and submitting a Photo Quiz manuscript can be found in the Authors' Guide at To be considered for publication, submissions must meet these guidelines. E-mail submissions to



Copyright © 2021 by the American Academy of Family Physicians.
This content is owned by the AAFP. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. This material may not otherwise be downloaded, copied, printed, stored, transmitted or reproduced in any medium, whether now known or later invented, except as authorized in writing by the AAFP. Contact for copyright questions and/or permission requests.

Want to use this article elsewhere? Get Permissions

CME Quiz

More in AFP

Editor's Collections

Related Content

More in Pubmed


May 2022

Access the latest issue of American Family Physician

Read the Issue

Email Alerts

Don't miss a single issue. Sign up for the free AFP email table of contents.

Sign Up Now

Navigate this Article