Analysis of factors favoring onset of fever after retrograde intrarenal surgery for kidney stones

Letterio D'Arrigo1, Francesco Savoca1, Angela Costa1, Astrid Bonaccorsi1, Antonio Cacciola1, Nazia Gill2, Ernst Witt2, Michele Pennisi1
  • 1 Ospedale Cannizzaro, U.O. Urologia (Catania)
  • 2 Statistic and probability Unit - Groningen University (Groningen)


The retrograde intrarenal surgery (RIRS) as alternative to percutaneous lithopaxy reduced incidence of postoperative complications. However postoperative fever still results in a high percentage of patients.
In this study we considered wich factors are related to persistent postoperative fever over 48 hours or urinary sepsis after RIRS.
Materials and Methodos

Materials and Methods

In the period between June 2012 and December 2013, 106 patients with urinary stones were treated with RIRS. A total of 115 procedures were performed.
Anagraphic data, stone burden and density, number of stones, operative time, kidney anatomic data (infundibular length, collector width, and infundibolopyelic angle), idronephrosis, preoperative presence of nephrostomy tube or double J and complication were evaluated. Stone burden and density stones were analyzed by preoperative noncontrast CT scan.
When more than one stone was present the diameter, volume and area was calculated like the sum of a single value.
All patients were preventively evaluated with blood and urine analysis and those with urinary infection were treated five days before surgery with specific antibiotics, the others with third generation cephalosporine or fluorchinolone preoperative prophylaxis.
All procedures were performed under general anesthesia and a semirigid ureterorenoscope with a 6/7.5F or 8/9.8 was used routinely for dilatation of the ureter passed over a hydrophilic guidewire. After an ureteral access sheath was placed. In all patients a flexible URS, with 200 micron holmium laser lithotripsy was used. We used a holmium-yag laser machine set at an energy level for stone fragmentation or pulverization according to type of urinary stone and choice of setting was entrusted to the operator on the basis of his experience. The operators were two urologists with the same experience having performed more than 50 flexible ureterorenoscopy. A double J stent was placed in every patient after procedure. If the operative time was over 90 min we stopped intervention and placed a double j.
We considered patients without stones or residual fragments below 4 mm after a three months treatment stone free. The software R was used for statistical analysis.


The SF was 77% after a single treatment (85% of stones <2 cm, 55% of stones> 2 cm). The persistent postoperative fever for more than 48 hours appered in 17 patients, therefore changed the antibiotic therapy (Clavien grade 2). The fever was serious in 5 patients, but intensive care wasn’t necessary.
Analysis of complication showed that fever had a higher incidence. In 17 (14.8%) patient cases out of 115, had postoperative fever for more than 48 hours (Clavien grade II). The operative time (p = 0.412), volume (p = 0.744), diameter (p = 0.975) and area (p = 0.176) did not influence the occurrence of sepsis. The presence of preoperative stent or nefrostomy favors onset fever (p = 0.01548) after RIRS. We also found two ureteral stenosis (Clavien grade III B) and one perirenal hematoma in a woman with hypotrophic kidney repeatedly treated in the past (Clavien III A). We found that patients who have DJ have higher probability of having sepsis, particularly in a younger patient. No patient needed to be admitted to intensive care unit.
Women have more probability of developing the fever than men and the older patients have less risk than the younger. This event was verified independently of nephrostomy or Dj.
The major complications were 2 ureteral stenosis (Clavien grade 3b) operated with laparoscopy and subcapsular hematoma (Clavien 3°) drained by percutaneous access, in a diabetic patient with hypotrophic kidney.


In our exploratory data analysis we had seen that patients with derivation DJ have an high probability of sepsis. Based on our gam model, we constructed a prediction table of sepsis, which shows the probability rates of patients having derivation DJ and non DJ.
It basically tells that females have high probability rates of having sepsis as compared to males. In addition to younger patients in both genders there is more chance of having sepsis. If a patient is 20 years old, if he is male he has a 40% probability rate of sepsis and if she is female she has a 64% probability of having sepsis. For the 80 year old patient sepsis rates are decreased in males to 4% and for female to 10%. We can see that in non DJ patient groups, women still have a higher probability of having sepsis. To explain this result we can said that some patients nefrostomy tube or double J for precedent sepsi in our or others hospitals were placed. This could be a favouring factor that could explain the high incidence of postoperative fever. A similar result was found in a recent study and the authors found a statistically significant high incidence of postoperative fever in patients with history of ureteroscopy after urinary decompression for urolithiasis related sepsis (25). Anyway there aren’t evident factors that could explain the major incidence in younger female.
Regarding to this complication we have seen that the operative time hasen’t influenced the onset of sepsi anyway in all cases were used the ureteral sheath with a constant flow irrigation to maintain a low intrarenal pressure.


The nefrostomy or DJ before operation favours the onset of fever in patients after RIRS and this is statistically significant (p=0.01548), even though the terapy or antibiotic prophylaxis is used.
Women and young patients develop postoperative fever more easily than older men.
Regarding to sepsi we have seen that the operative time hasen’t influenced the onset of sepsi. Anyway in all cases were used the ureteral sheath with a constant flow irrigation to maintain a low intrarenal pressure. This precaution don’t explain perirenal ematoma that was observed. Regarding to this complication we think that is related to renal hypotrophy and to particular condition of kidney. Probably a low compliance of pielocaliceal system related to previous infections could explain the onset of this complication.
A correct preoperative evaluation of the patient, related risk factors, and analysis of urine are important. Adequate preoperative antibiotic prophylaxis to prevent the development of infections and advers events, can limit the onset of complications.
More studies are needed to explain the higher incidence of fever in younger female patients.


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