The aim of the study is to evaluate the predictors of success of oral dissolution therapy in radiolucent renal stones in a large series of patients from a tertiary referral center in order to define the optimum case scenarios where oral dissolution therapy could be implemented.

Patients with renal stones, seen through the outpatient clinic in the urology department or post primary intervention for renal stones, will be assessed to see if the patient satisfies all inclusion and exclusion criteria. Patients who are meeting these criteria will be asked to participate in this prospective study. If they agree, they will be asked to sign an informed consent.

Baseline patients' assessment will include;

• Full history taking including

  • Previous stone history regarding presentation and management
  • Previous trial oral dissolution therapy for renal stones and their compliance to the treatment
  • Previous GIT surgery
  • History of chronic medical or metabolic illness e.g; DM

• Clinical examination including

  o Body mass index (BMI)

• Laboratory investigations including;

  • Urine analysis (urine PH)
  • 24 hours urine testing for uric acid and citrate
  • Urine culture
  • Serum creatinine
  • Random blood sugar (RBS)
  • Serum uric acid
  • Serum calcium, phosphorus and magnesium.

• Initial radiological evaluation will include

  • Renal ultrasonography (US)
  • Plain X-rays to exclude the presence of calcification in the targeted stone.
  • Non Contrast Computed Tomography (NCCT) on the abdomen and pelvis.
  • MAG3 diuretic renogram

(All NCCT studies will be performed with multislice helical CT scanners, NCCT images will be obtained from above the kidneys through the bladder base. For each renal stone, its location will be recorded, its size will be measured using the largest dimension from length (L), width (W) and height (H) on axial and coronal reformat images. Its mean density will be recorded by measurement using region of interest just smaller than the stone. Associated hydronephrosis proximal to the stone will be also evaluated (Nakada et al 2000).)

Patient will receive the allocated instructions and medications

Patients' follow up (The aim at follow up is to monitor the urinary PH with adjustment of the dose of potassium citrate and also to assess the compliance of the patients regarding the dietary recommendations and the medications)

• After 2 weeks, 4 weeks, 8 weeks and 12 weeks.

  - the most important parameter will be assessed is the urinary PH every two weeks. The target urinary PH should be kept between6.5 to 7.0, the dose of potassium citrate should be adjusted to achieve this value.

• Patients' compliance to medications intake and the instruction of fluid intake and dietary modification.

Inclusion Criteria:

• Patients' criteria:

  1. Ability to give informed consent.
  2. Age more than 18 years.
  3. Absence of significant hydronephrosis, serious urinary tract infection, congenital anomalies or distal ureteric obstruction in the affected renal unit.
  4. Normal cardiac, hematological, and renal functions.

• Stone criteria:

  1. Primary or recurrent renal stone.
  2. Patients with residual renal stones after primary intervention whether open surgery, endoscopic or ESWL.
  3. Peripheral calyceal stones or stone in the renal pelvis with no significant hydronephrosis.
  4. Stone size less than 3 cm in maximum diameter
  5. Stones with radiodensity less than 600 Hounsefield units attenuation in Non Contrast Computed Tomography (NCCT).

Exclusion Criteria:

• Patients' criteria:

  1. Inability to give informed consent.
  2. Age less than 18 years
  3. Patients with unremitting pain or serious urinary tract infection.
  4. Presence of significant hydronephrosis, congenital anomalies or distal ureteric obstruction in the affected renal unit.
  5. Abnormal cardiac, hematological or renal functions.

• Stone criteria:

  1. Obstructing stone in the renal pelvis with significant hydronephrosis.

  2. Assumption of presence of calcium stones by presence of calcification in the stone in plain X-rays.

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