tuberous sclerosis complex ( tsc ) is a genetic disorder that can affect almost all organ systems .
renal manifestations occur with high frequency , the most prevalent being angiomyolipoma ( aml ) .
tsc - associated amls tend to be larger , more numerous , and more likely to cause spontaneous hemorrhage compared with sporadic amls .
removal of renal calculi from kidneys with amls is particularly difficult because these tumors increase the potential for hemorrhage .
we report the case of a 65-year - old man with tsc - associated aml and a renal calculus greater than 4 cm in his left kidney .
the calculus was successfully removed by retrograde flexible ureterorenoscopy ( f - urs ) with holmium laser lithotripsy .
he was previously diagnosed with tsc after being identified with the typical features , such as dermatological lesions ( facial angiofibroma , ungual fibromas , and hypomelanotic macules on the toes ) , subependymal nodules , and multiple amls in both kidneys . while there was no family history of tsc , the patient had childhood epilepsy .
he also experienced two episodes of hypovolemic shock concomitant with extensive retroperitoneal hemorrhage caused by spontaneous aml rupture , once in each kidney .
following the second episode , which occurred in the left kidney , he developed sepsis caused by staphylococcus aureus , which was isolated from both venous blood and urine .
blood counts were within normal limits except for a low red blood cell count ( 331  10/mm ; normal , 430  10570  10/mm ) , low hemoglobin ( 9.5 g / dl ; normal , 13.517.0 g / dl ) , and a low hematocrit value ( 30.4% ; normal , 40%50% ) .
serum creatinine level was 1.0 mg / dl ( normal , 0.61.1 mg / dl ) .
ureter  bladder ( kub ) radiography revealed a 43  16 mm renal calculus in the left kidney [ figure 1a ] .
intravenous pyelography revealed that the calculus filled the pelvis and lower calyx , causing dilatation of the upper calyx [ figure 1b ] .
abdominal enhanced computed tomography ( ct ) demonstrated a significant bilateral renal aml burden in addition to the renal calculus in the left kidney [ figure 2 ] .
we decided to remove the renal calculus for several reasons , including the present clinical symptoms and a previous history of urinary tract infection .
minimally invasive retrograde f - urs with holmium laser lithotripsy was chosen because multiple renal amls have hemorrhagic potential .
( a ) kub radiography reveals a lower pole renal calculus in the left kidney .
( b ) intravenous pyelography shows the calculus causing dilatation of the upper calyx abdominal enhanced computed tomography demonstrates significant bilateral renal aml burden and a large renal calculus in the left kidney a 6.9-fr f - urs , a 10-fr ureteral access sheath , and a 200- holmium : yag laser fibers were used for treatment .
we attempted to vaporize the stone by  painting  the laser fiber over the stone surface .
a 1.9-fr nitinol basket , which minimizes the loss of deflection during f - urs , was used to extract large fragments and reposition them from the lower pole calyx into a position more readily accessible by the laser fiber , such as the renal pelvis or upper pole calyx .
no evidence of greater than 2-mm residual stones was observed before removal of the ureteral stent in postoperative kub radiography .
three months after surgery , kub radiography confirmed the absence of any residual stones [ figure 3 ] , and urinalysis was also revealed normal findings .
three months after flexible ureterorenoscopy , follow - up kub radiography confirms the absence of any residual stones
rakowski et al . reported renal lesions in 57.5% tsc patients ; of these , aml was present in 85.4% , cysts in 44.8% , and renal cell carcinoma in 4.2% .
tsc - associated aml is more likely to cause spontaneous hemorrhage compared with its sporadic counterpart , with a hemorrhagic risk of 25% to 50% .
tsc patients are also predisposed to nephrolithiasis because of both the disease and its treatments . for example , drugs like topiramate have proven to be effective for some forms of tsc - associated epilepsy ; however , they also increase the risk of nephrolithiasis .
patients are also at higher risk for renal cystic disease because disruption of distal tubular function by a significant cyst burden leads to hypocitraturia .
our patient was not undergoing any treatment for epilepsy , and ct demonstrated no evidence of renal cystic lesions .
traditional surgical treatment of renal calculi , including minimally invasive procedures like percutaneous nephrolithotomy ( pnl ) or extracorporeal shockwave lithotripsy ( eswl ) , may lead to bleeding in patients with renal amls .
pnl remains a milestone technique with a high success rate and with a low percentage of major complications ; however , the blood transfusion rate reported varies from 11.2% to 17.5% .
pnl involves puncture and dilation of the renal collecting system via the renal parenchyma and poses an unacceptable risk of hemorrhage in kidneys with aml , although there are two reported cases of pnl performed directly through a renal aml . on the other hand , eswl requires large numbers of shock waves , which can lead to capillary damage with parenchymal or subcapsular hemorrhage ; eswl - induced retroperitoneal bleeding has been reported in a patient with renal aml .
recent studies have evaluated f - urs as an alternative treatment for patients with contraindications to pnl or eswl , such as pregnant woman , obese patients , or those with coagulopathy .
indeed , f - urs using pulsed laser energy can fragment stones with less risk of hemorrhage . furthermore , f - urs is a minimally invasive procedure that can treat < 2-cm renal calculi with a low morbidity and high success rate .
our case and other reported cases indicate that f - urs can also safely treat larger stones .
however , the management of lower pole renal calculi with f - urs remains debatable because of limited access and poor clearance of stone fragments . by the current literature
, pnl should be considered the first line of treatment for greater than 2-cm lower pole renal calculi .
further advances in endoscopic technology and techniques are required to resolve the limitations of f - urs , including the technical difficulty in removing large stones , intrarenal influx with infected stones , and prolonged surgical duration . in conclusion ,
retrograde f - urs with holmium laser lithotripsy is an effective , minimally invasive therapy for patients at high risk of renal hemorrhage .
 renal calculi in patients with renal angiomyolipomas are difficult to treat because of the hemorrhagic potential of these tumors . 
 we describe the case of a 65-year - old man having tuberous sclerosis complex - associated multifocal renal angiomyolipomas with a large renal calculus . the patient presented with left flank dullness and a previous history of spontaneous angiomyolipoma rupture . 
 intravenous pyelography revealed a 43  16 mm calculus in the pelvis and lower calyx of the left kidney . 
 the calculus was successfully removed by retrograde flexible ureterorenoscopy and holmium - yag lithotripsy . 
 flexible ureterorenoscopy is an effective , minimally invasive therapy for patients at high risk of renal hemorrhage . 
INTRODUCTION
CASE REPORT
DISCUSSION