Differential Diagnosis for R Flank Pain and Foul Smelling Urine
Given the symptoms of right flank pain and foul-smelling urine for 1 week, with normal retrograde ultrasound (US) and normal urinalysis, the differential diagnosis can be categorized as follows:
Single Most Likely Diagnosis
- Urinary Tract Infection (UTI) not detected by standard urinalysis: This could be due to an infection with an organism that does not reduce nitrate to nitrite (e.g., some strains of Staphylococcus saprophyticus), or an early infection where the bacterial load is not yet sufficient to cause a positive urinalysis. The foul-smelling urine is a strong clue towards a UTI.
Other Likely Diagnoses
- Kidney Stone (with normal US due to small size or location not easily visualized): Small stones or those in certain locations might not be detected by ultrasound. The flank pain could be indicative of a stone, even if the urinalysis and US are normal.
- Interstitial Cystitis: This condition can cause foul-smelling urine and flank pain due to bladder inflammation, without necessarily showing abnormalities on urinalysis or US.
- Prostatitis (in males): Could cause flank pain and foul-smelling urine due to prostate inflammation, potentially with normal urinalysis if the infection is not severe enough to alter urine test results.
Do Not Miss Diagnoses
- Pyelonephritis: An infection of the kidney, which could present with flank pain and foul-smelling urine. It's crucial to diagnose and treat promptly to prevent complications like sepsis or kidney damage.
- Appendicitis (if the pain is more lower quadrant than flank): Although less likely given the description of flank pain, appendicitis can sometimes present with urinary symptoms if the appendix is located near the urinary tract.
- Tuberculosis of the Urinary Tract: A chronic infection that can cause flank pain and alterations in urine smell, with potentially normal or intermittently abnormal urinalysis.
Rare Diagnoses
- Malacoplakia: A rare condition characterized by the formation of plaques in the urinary tract due to a chronic infection, which could cause foul-smelling urine and flank pain.
- Foreign Body in the Urinary Tract: Could cause infection and foul-smelling urine, though this would be an unusual cause of the symptoms described.
- Fistula between the Urinary Tract and the Intestine: Would allow fecal material to enter the urinary tract, causing foul-smelling urine, but this is a rare condition often associated with other symptoms like recurrent UTIs or pneumaturia.