Imaging and Management of Right Flank Pain

Initial Evaluation

The American College of Radiology recommends using ultrasound as the first-line imaging modality for patients presenting with right flank pain, followed by non-contrast CT if diagnosis remains unclear or if urolithiasis is strongly suspected but not visualized on ultrasound 1
Ultrasound is recommended as the initial imaging modality because it allows for evaluation of both kidneys and bladder in one examination, and it is cost-effective compared to CT, with a high sensitivity for detecting hydronephrosis 2
The American Academy of Family Physicians recommends ultrasound as the imaging modality of choice for initial evaluation, with a rating of 8 - usually appropriate, and a rating of 7 - usually appropriate for pregnant patients 3

Use both longitudinal and transverse views of the kidneys, and employ color Doppler to assess for "twinkling artifact," which can help identify stones, although ultrasound may miss stones smaller than 3 mm, and hydronephrosis may be masked by dehydration 2
Absence of hydronephrosis does not rule out ureteral stones, and medullary pyramids may mimic hydronephrosis, especially in young patients 2

Abdominal aortic aneurysm may present with symptoms mimicking renal colic, and should be considered as an alternative diagnosis when evaluating right flank pain with ultrasound, along with other non-urological causes of flank pain, such as right colonic diverticulitis, bowel obstruction, musculoskeletal causes, gynecological conditions, and renal infarction or other vascular pathologies 2, 4

Non-contrast CT scan is the gold standard for confirming stone presence, size, and location, with superior sensitivity (93-97%) and specificity (96.6%), as recommended by the American College of Radiology 1
CT urography is highly valuable for comprehensive evaluation, including unenhanced images followed by IV contrast-enhanced nephrographic and excretory phases, allowing for near-comprehensive evaluation of the genitourinary tract, with a 100% detection rate for renal calculi in patients with renal colic or hematuria, as recommended by the American College of Radiology 5

Increased fluid intake to achieve at least 2L of urine output per day is the most important preventive measure, and first-line pain control with NSAIDs is recommended for patients with flank pain likely due to recurrent kidney stones, as recommended by the American College of Internal Medicine 6
Allopurinol is suggested for uric acid stones or calcium stones with hyperuricosuria, as recommended by the American College of Internal Medicine 6
NSAIDs (such as diclofenac, ibuprofen, or metamizole) are recommended as the first-line medication for patients with ongoing flank pain after passing a kidney stone, as they are more effective than opioids for renal colic and reduce the need for additional analgesia, as recommended by the European Urology guidelines 7
Opioid analgesics are reserved for cases where NSAIDs are contraindicated or ineffective, according to the BMJ guidelines 8

Increased fluid intake, with a target urine output >2L/day, is recommended to prevent future stone formation, as supported by the European Urology guidelines 7
Dietary modifications based on stone composition, such as moderate calcium intake, reduced sodium and animal protein for calcium stones, and reduced purine intake for uric acid stones, are suggested, as supported by the European Urology guidelines 7
Follow-up urinalysis to confirm resolution of hematuria and consideration of metabolic testing for high-risk patients are recommended, according to the European Urology guidelines 7
Patients with persistent hematuria require continued surveillance to exclude underlying malignancy or other conditions, with recommended follow-up at 6, 12, 24, and 36 months, including urinalysis, urine cytology, and blood pressure checks, and immediate re-evaluation if gross hematuria, abnormal cytology, or new symptoms develop 9, 10, 11

Immediate referral is indicated for patients with persistent severe pain despite adequate analgesia, signs of infection, hydronephrosis on imaging, solitary kidney with persistent symptoms, or recurrent stone formation, as recommended by the BMJ and European Urology guidelines 7, 8
Referral to a urologist or other specialist is recommended for patients with complex stone disease, underlying anatomical abnormalities, or other conditions requiring specialized care, as supported by the European Urology guidelines 7
Conservative management with increased fluid intake, pain control with NSAIDs, and follow-up imaging in 2-4 weeks is recommended for small stones (<5mm) without obstruction, as suggested by the BMJ guidelines 8
Urological intervention, such as ureteroscopy, extracorporeal shock wave lithotripsy, or percutaneous nephrolithotomy, should be considered for larger stones (>5mm) or stones causing obstruction, according to the European Urology guidelines 7