Purpose To evaluate whether the neutrophil-to-lymphocyte ratio (NLR) can predict the need for ureteral catheterization in patients with renal colic. Materials and methods We retrospectively studied 15,887 patients with renal colic between 2005 and 2019. Patients with prior antibiotics treatment (156), with hematological diseases (15), with negative computerized tomography scan (CTS) for stone disease (473) or with no available laboratory findings (1750) were excluded. A ureteral double J stent (DJS) was inserted in case of ongoing pain, fever, sepsis, single kidney and elevated blood creatinine levels concomitant with hydronephrosis. A cut-off value of 2.1 NLR was determined to stratify and to compare patients using multivariable logistic regression models. A locally weighted scatterplot smoothing (LOWESS) plot was also applied to show the relationship between NLR and predicted probability for DJS insertion. Results Thirteen-thousand and 493 patients with a mean age of 42.7 years (30% females and 70% males) were included in the study. Five-hundred and 57 patients (4.1%) underwent early DJS insertion: 5.3% vs. 1.5% of patients with high vs. low NLR, respectively, (p<0.001). High NLR was significantly associated with longer hospitalization time, admission to the intensive care unit and overall mortality within a month from admission (p<0.05). LOWESS plot showed that NLR value >2.1 escalates progressively the probability for DJS insertion. Conclusions A high NLR is associated with the need for early internal DJS insertion due to urolithiasis. The NLR is easily calculated from simple blood tests and based on our results can be used for clinical decision making in patients with renal colic needing renal decompression.