GU Numbers to Know
Key Points
- This is the genitourinary reference card: every threshold, grade, normal value, and accuracy figure the GU pages state, in one place, worded as the source states them.
- Adrenal: ≤10 HU unenhanced, or absolute washout ≥60% and relative washout ≥40%, means adenoma; ≥4 cm with no benign features goes to surgery.
- Renal mass: −10 to +20 HU homogeneous is a simple cyst; ≥70 HU unenhanced is a hyperdense cyst; fat below −10 HU is angiomyolipoma; Bosniak v2019 turns on 2 mm, 3 mm, and 4 mm walls and septa.
- Prostate: 1.5 cm separates PI-RADS 4 from 5; DWI rules the peripheral zone and T2 the transition zone.
- Scrotum: a testis is about 5 × 3 × 2 cm, and Doppler ultrasound is 0.86 sensitive and 0.95 specific for torsion.
Every GU rotation ends with the same scrap of paper folded into a coat pocket, covered in Hounsfield units and millimeters that somebody swore would be on the boards. This page is that scrap of paper, except every line on it is traceable to a named source. Skim it before a call shift, or use each section's link to go back to the page that teaches the idea behind the number.
Adrenal
Taught on adrenal adenoma versus metastasis: washout and myelolipoma, pheochromocytoma, and carcinoma.
| What | Value | Context |
|---|---|---|
| Unenhanced CT attenuation diagnostic of a lipid-rich adrenal adenoma | ≤10 HU | Homogeneous mass on unenhanced CT; considered diagnostic regardless of size; no further imaging needed (ACR 2017). Same threshold used by Caoili et al. |
| Performance of unenhanced CT attenuation thresholds for calling an adrenal mass benign | Sensitivity 47% at a 2 HU threshold rising to 88% at 20 HU; specificity 100% at 2 HU falling to 84% at 20 HU | Pooled analysis of 10 CT reports, 495 adrenal lesions (272 benign, 223 malignant). 10 HU is the conventional compromise between the two |
| Absolute percentage washout (APW) diagnostic of adenoma | ≥60% | APW = (enhanced HU − 15-min delayed HU) / (enhanced HU − unenhanced HU) × 100, on a dedicated adrenal-protocol CT |
| Relative percentage washout (RPW) diagnostic of adenoma | ≥40% | RPW = (enhanced HU − 15-min delayed HU) / enhanced HU × 100; used when an unenhanced value is not available |
| Dedicated adrenal-protocol CT | Unenhanced acquisition reviewed in real time; if no benign features, dynamic contrast-enhanced phase at 60–90 s after power injection, then a 15-min delayed acquisition | Recommended collimation 3 mm with axial and coronal reconstructions; 120 kVp suggested for density measurement; unenhanced series at reduced dose with limited z-axis coverage |
| Definition of a non-enhancing adrenal mass (cyst or hemorrhage) | <10 HU change | Change between pre- and post-contrast attenuation; such masses need no further workup or follow-up |
| Diagnostic benign feature: macroscopic fat | Presence of macroscopic fat indicates myelolipoma; no additional workup or follow-up imaging | Alongside cyst, hemorrhage, and benign calcified masses as 'diagnostic benign imaging features' |
| Chemical-shift MRI sign of a lipid-rich adenoma | Signal loss on opposed-phase compared with in-phase images, judged against the spleen | Almost always diagnostic of lipid-rich adenoma regardless of size; MRI can characterize adenomas when CT is indeterminate |
| Indeterminate adrenal mass 1 to <4 cm and >10 HU | Dedicated adrenal-protocol CT (density plus washout) is the imaging examination of choice | ACR 2017 algorithm |
| Isolated adrenal mass ≥4 cm without benign diagnostic features or cancer history | Surgical resection (without biopsy) recommended to treat possible adrenocortical carcinoma | ACR 2017 algorithm |
| Growth-rate threshold separating benign from malignant adrenal masses | None established | Both benign and malignant adrenal masses may enlarge; enlarging indeterminate masses go to biochemical evaluation and, depending on growth, resection |
| Central necrosis in an adrenal mass | Raises the likelihood of metastasis; biopsy or PET/CT may be considered | ACR 2017 |
| Combined unenhanced plus delayed-enhanced CT for adenoma vs non-adenoma | Nearly all adrenal masses correctly categorized (166 masses: 127 adenomas, 39 non-adenomas) | Adenoma called when unenhanced attenuation ≤10 HU or percentage washout ≥60% |
Renal mass attenuation and enhancement
Taught on approach to the renal mass, renal masses, and angiomyolipoma and oncocytoma.
| What | Value | Context |
|---|---|---|
| Macroscopic fat in a renal mass (angiomyolipoma) | < −10 HU | A region of interest measuring fat attenuation; ACR flowchart for fat-containing masses |
| Simple renal cyst on CT | Homogeneous, −10 to +20 HU, without enhancement (Bosniak I); needs no further evaluation | Applies whether the CT was without or with contrast; a homogeneous mass under 20 HU is rarely RCC, which is almost always heterogeneous unenhanced |
| Homogeneous renal mass ≥70 HU on unenhanced CT | Almost always a hyperdense (Bosniak II) cyst; no further evaluation | On contrast-enhanced CT both RCC and hyperdense cysts may measure ≥70 HU, so the rule applies to unenhanced CT only |
| Homogeneous renal mass that needs pre- and post-contrast characterization | >20 and <70 HU on unenhanced CT, or >20 HU on a contrast-enhanced-only CT | Enhancement of the mass or of any nodular component is concerning for neoplasm |
| "Too small to characterize" (TSTC) renal mass | A mass too small to measure attenuation accurately; well-circumscribed homogeneous TSTC masses visually much lower (or, unenhanced, much higher) than renal parenchyma are probably benign cysts | MRI is preferred for characterizing masses <1.5 cm and for detecting enhancement in suspected hypovascular masses |
| Likelihood that a solid renal mass is benign, by size | <1 cm ≈40%; 1–4 cm ≈20%; >4 cm <10% | Smaller cancers are also more likely to be indolent with lower metastatic risk |
| Stable renal mass (no further workup) | No change in imaging features and average growth ≤3 mm per year for at least 5 years | Growth is defined as ≥4 mm per year on average; morphologic change is any change in heterogeneity such as contour, attenuation, or number of septa |
| Angiomyolipoma: referral for prophylactic treatment | AML ≥4 cm, or an aneurysm >0.5 cm | Symptomatic AML (hematuria, flank pain, spontaneous bleeding) is referred regardless of size. The 4 cm cutoff traces to Oesterling et al. (1986) |
Bosniak v2019
Taught on simple versus complex cysts: Bosniak. Version: Bosniak classification of cystic renal masses, v2019.
| What | Value | Context |
|---|---|---|
| Bosniak I | Well-defined, thin (≤2 mm) smooth wall; homogeneous simple fluid (−9 to 20 HU); no septa or calcification; the wall may enhance | Benign; no follow-up |
| Bosniak II | Well-defined thin (≤2 mm) smooth walls, with any of: few (1–3) thin (≤2 mm) septa (may enhance; calcification of any type allowed); homogeneous hyperattenuating (≥70 HU) mass on unenhanced CT; homogeneous non-enhancing mass >20 HU (may have calcification); homogeneous −9 to 20 HU on unenhanced CT; homogeneous 21–30 HU on portal venous phase CT; homogeneous low-attenuation mass too small to characterize | Benign; no follow-up |
| Bosniak IIF | Smooth minimally thickened (3 mm) enhancing wall, or minimal thickening (3 mm) of one or more smooth enhancing septa, or many (≥4) smooth thin (≤2 mm) enhancing septa | Follow-up imaging |
| Bosniak III | One or more enhancing thick (≥4 mm width) or enhancing irregular (≤3 mm obtusely margined convex protrusions) walls or septa | Indeterminate; roughly half are malignant (as summarized); urologic referral |
| Bosniak IV | One or more enhancing nodules: a ≥4 mm convex protrusion with obtuse margins, or a convex protrusion of any size with acute margins | Roughly 90% malignant (as summarized); treatment for appropriate candidates |
RCC staging
Taught on RCC subtypes and staging. Version: AJCC Cancer Staging Manual, 8th edition.
| What | Value | Context |
|---|---|---|
| Renal cell carcinoma T category (AJCC 8th ed.) | T1a ≤4 cm and T1b >4 to ≤7 cm, confined to the kidney; T2a >7 to ≤10 cm and T2b >10 cm, confined to the kidney; T3a: extends into the renal vein or its segmental branches, or invades the pelvicalyceal system, or invades perirenal and/or renal sinus fat but not beyond Gerota fascia; T3b: extends into the vena cava below the diaphragm; T3c: above the diaphragm or invades the wall of the vena cava; T4: beyond Gerota fascia, including contiguous extension into the ipsilateral adrenal gland | Size cutoffs apply to tumors confined to the kidney; T3 and T4 are defined by what is invaded, not by size |
Urolithiasis
Taught on ureteral stones and complications and urolithiasis.
| What | Value | Context |
|---|---|---|
| Unenhanced helical CT for ureteral stone in acute flank pain | Sensitivity 97%, specificity 96%, accuracy 97% | Smith et al., 1996 |
| Spontaneous ureteral stone passage by size (guideline meta-analysis) | ≤5 mm: 68% (95% CI 46–85%); >5 to ≤10 mm: 47% | Meta-analysis of observation-arm patient groups (224 and 104 patients respectively) |
| Spontaneous ureteral stone passage by CT-measured size | 1 mm 87%; 2–4 mm 76%; 5–7 mm 60%; 7–9 mm 48%; >9 mm 25% | Coll et al., 2002 |
| Spontaneous ureteral stone passage by location | Proximal ureter 48%; mid ureter 60%; distal ureter 75%; ureterovesical junction 79% | Coll et al., 2002 |
CT urography
Taught on CT and MR urography protocols and urothelial cancer.
| What | Value | Context |
|---|---|---|
| CT urography for upper tract urothelial carcinoma in patients with hematuria | Pooled sensitivity 96% (95% CI 88–100%); pooled specificity 99% (95% CI 98–100%) | Systematic review and meta-analysis, Chlapoutakis et al., 2010 |
| CT urography phase strategy (ESUR guideline) | Either a combined nephrographic–excretory phase after a split-bolus injection, or separate nephrographic and excretory phases after a single bolus | Optional low-dose unenhanced series on indication |
| CT urography dose bands (ESUR guideline) | CTDIvol 5–6 mGy for benign conditions; 9–12 mGy for potential malignant disease; optional unenhanced series at 2–3 mGy | ESUR CT urography working group |
VI-RADS
Taught on bladder cancer and VI-RADS. Version: VI-RADS 2018.
| What | Value | Context |
|---|---|---|
| VI-RADS 1 | Lesion <1 cm with a continuous low-signal line of muscularis propria on T2W (with or without stalk or thickened inner layer); muscularis line intact on DCE and DWI | Muscle invasion highly unlikely |
| VI-RADS 2 | Lesion >1 cm with a continuous low-signal muscularis line: papillary tumor with a stalk, or sessile tumor with a thickened high-signal inner layer; muscularis line intact on DCE and DWI | Muscle invasion unlikely |
| VI-RADS 3 | No stalk (papillary) or no high-signal thickened inner layer (sessile) but the low-signal muscularis line is still continuous | Equivocal for muscle invasion |
| VI-RADS 4 | Interruption of the low-signal muscularis propria line on T2W; focal extension of early enhancement (DCE) or of tumor (DWI) into the muscularis propria | Muscle invasion likely |
| VI-RADS 5 | Tumor extends through the entire bladder wall into perivesical fat on T2W, DCE, and DWI | Invasion of muscle and beyond the bladder very likely |
| VI-RADS final scoring rule | If T2W and DWI disagree, DWI is the dominant sequence; if DWI is suboptimal, DCE becomes the dominant sequence | Panebianco et al., 2018 |
Renal infection
Taught on the renal infection spectrum and pyelonephritis.
| What | Value | Context |
|---|---|---|
| Emphysematous pyelonephritis, Huang–Tseng CT classification | Class 1: gas in the collecting system only; Class 2: gas in the renal parenchyma without extension to the extrarenal space; Class 3A: extension of gas or abscess to the perinephric space; Class 3B: extension of gas or abscess to the pararenal space; Class 4: bilateral EPN, or EPN in a solitary kidney | Higher class correlates with worse outcome; class 1 has the best prognosis |
Renal vascular and transplant
Taught on renal infarct and vascular disease and renal transplant imaging. The normal kidney dimensions sit here too, because they are the baseline for every vascular and transplant study.
| What | Value | Context |
|---|---|---|
| Doppler thresholds for renal artery stenosis | Peak systolic velocity 180 cm/s and renal–aortic ratio 3.0 (optimal by ROC analysis) | Combined, sensitivity 85% and specificity 76% in this series |
| Renal allograft intrarenal resistive index | ≥0.80 | RI = (peak systolic − end-diastolic velocity) / peak systolic velocity. At or above 0.80 was associated with higher recipient mortality but not with graft loss or need for dialysis; it reflects the recipient more than the graft |
| Adult kidney length and volume at sonography | Median length 11.2 cm (left) and 10.9 cm (right); median volume 146 cm³ (left) and 134 cm³ (right) | 665 adult volunteers; dimensions vary with age, sex, and body habitus |
Renal trauma (AAST 2018)
Taught on renal trauma and the AAST scale. Version: AAST organ injury scale, 2018 update.
| What | Value | Context |
|---|---|---|
| AAST kidney injury grade I | Subcapsular hematoma and/or parenchymal contusion without laceration | Imaging criteria column |
| AAST kidney injury grade II | Perirenal hematoma confined to Gerota fascia; or renal parenchymal laceration ≤1 cm depth without urinary extravasation | Imaging criteria column |
| AAST kidney injury grade III | Renal parenchymal laceration >1 cm depth without collecting system rupture or urinary extravasation; or any injury in the presence of a kidney vascular injury or active bleeding contained within Gerota fascia | Imaging criteria column |
| AAST kidney injury grade IV | Parenchymal laceration extending into the urinary collecting system with urinary extravasation; renal pelvis laceration and/or complete ureteropelvic disruption; segmental renal vein or artery injury; active bleeding beyond Gerota fascia into the retroperitoneum or peritoneum; segmental or complete kidney infarction(s) due to vessel thrombosis without active bleeding | Imaging criteria column |
| AAST kidney injury grade V | Main renal artery or vein laceration or avulsion of the hilum; devascularized kidney with active bleeding; shattered kidney with loss of identifiable parenchymal renal anatomy | Imaging criteria column |
| AAST 2018 grading rules and vascular definitions | Grade by the highest grade assessed on imaging, at operation, or on pathology; more than one grade may be present and is classified by the higher; advance one grade for multiple injuries up to grade III. Vascular injury = pseudoaneurysm or arteriovenous fistula (focal contrast collection that decreases in attenuation on delayed imaging); active bleeding = vascular contrast that increases in size or attenuation on the delayed phase | AAST 2018 update |
Urinary tract dilation
Taught on hydronephrosis and obstruction.
| What | Value | Context |
|---|---|---|
| UTD classification, antenatal (anteroposterior renal pelvic diameter) | Normal: <4 mm at 16–27 weeks, <7 mm at ≥28 weeks. UTD A1 (low risk): 4 to <7 mm at 16–27 weeks or 7 to <10 mm at ≥28 weeks, with or without central calyceal dilation. UTD A2–3 (increased risk): ≥7 mm at 16–27 weeks or ≥10 mm at ≥28 weeks, or peripheral calyceal dilation, ureteral dilation, parenchymal abnormality, or bladder abnormality | Multidisciplinary consensus, 2014 |
| UTD classification, postnatal | UTD P1 (low risk): APRPD 10 to <15 mm and/or central calyceal dilation. UTD P2 (intermediate): APRPD ≥15 mm or peripheral calyceal dilation. UTD P3 (high risk): ureteral dilation, parenchymal abnormality (thinning, abnormal echogenicity, cysts), or bladder abnormality, regardless of APRPD | Classification is driven by the most concerning finding |
| Society for Fetal Urology (SFU) hydronephrosis grades | Grade 1: slight separation of the central renal echo complex (pelvis only). Grade 2: pelvis further dilated with a single or a few calyces seen. Grade 3: pelvis dilated with fluid-filled calyces throughout the kidney, parenchyma of normal thickness. Grade 4: as grade 3 but the parenchyma over the calyces is thinned | Fernbach et al., 1993 |
Prostate (PI-RADS v2.1)
Taught on prostate MRI, prostate cancer staging with mpMRI, and BPH. Version: PI-RADS v2.1 (2019).
| What | Value | Context |
|---|---|---|
| PI-RADS v2.1 assessment categories | 1 very low (clinically significant cancer highly unlikely); 2 low (unlikely); 3 intermediate (equivocal); 4 high (likely); 5 very high (highly likely) | One category per lesion |
| PI-RADS v2.1 dominant sequences | Peripheral zone: DWI/ADC is the dominant sequence. Transition zone: T2-weighted imaging is the dominant sequence | Decides which score becomes the category |
| PI-RADS v2.1 upgrade rules | Peripheral zone DWI score 3 becomes category 4 if DCE shows focal early enhancement, otherwise stays 3. Transition zone T2 score 3 becomes category 4 if DWI is 5, otherwise stays 3; transition zone T2 score 2 becomes category 3 if DWI is ≥4 | The secondary sequences only move a category at these points |
| PI-RADS v2.1 size threshold between scores 4 and 5 | Score 4: <1.5 cm in greatest dimension. Score 5: ≥1.5 cm, or definite extraprostatic extension or invasive behavior | Size or invasion, not signal, separates 4 from 5 |
| PI-RADS v2.1 technical minimums used in scoring | High b-value DWI of ≥1400 s/mm² (acquired or calculated); DCE temporal resolution ≤15 s | Required for the DWI and DCE scores to be applied |
| Prostate volume (ellipsoid formula) | Maximum anteroposterior × longitudinal (mid-sagittal T2W) × transverse (axial T2W) diameters × 0.52 | Reported on every prostate MRI |
| PI-RADS v2 for detection of prostate cancer (meta-analysis) | Pooled sensitivity 89%, pooled specificity 73% | 21 studies, 3857 patients; PI-RADS version 2 (the predecessor of v2.1) |
Scrotum
Taught on scrotal ultrasound, testicular torsion, epididymo-orchitis, scrotal trauma, and testicular tumors.
| What | Value | Context |
|---|---|---|
| Normal adult testis | About 5 × 3 × 2 cm; homogeneously echogenic; regresses with age | Grayscale ultrasound |
| Normal epididymal head | 10–12 mm in diameter (the largest part of the epididymis) | Grayscale ultrasound |
| Normal fluid between the layers of the tunica vaginalis | 2–3 mL | More than this is a hydrocele |
| Proposed pampiniform vein diameter cut-offs for varicocele | 2.5 mm at rest; 3.0 mm with Valsalva | Proposed by some authors; ultrasound about 97% sensitive and 94% specific for varicocele (as summarized) |
| Ultrasound (color Doppler) for testicular torsion in adults (meta-analysis) | Overall sensitivity 0.86 (95% CI 0.79–0.91), specificity 0.95 (0.92–0.97); studies after 2010: sensitivity 0.95 (0.84–0.99), specificity 0.98 (0.93–0.99) | Ota et al., 2019 |
| Whirlpool sign (twisted spermatic cord) for torsion | Sensitivity 92%, specificity 99% (as summarized) | Grayscale and color Doppler of the cord |
| Ultrasound for epididymitis | Sensitivity 70%, specificity 88% (as summarized) | A normal-looking epididymis does not exclude it |
| Ultrasound for testicular rupture after blunt trauma | Sensitivity 100%, specificity 93.5% (65 patients) using heterogeneous testicular echotexture plus contour abnormality; across series, sensitivity 64–100% and specificity 65–93.5% | Buckley and McAninch, 2006; ranges as summarized |
| Testicular microlithiasis follow-up (ESUR guideline) | No follow-up for isolated microlithiasis without risk factors; annual ultrasound up to age 55 when risk factors are present (personal or family history of germ cell tumor, maldescent, orchidopexy, testicular atrophy); microlithiasis with a testicular mass warrants urgent specialist referral | Richenberg et al., 2015 |
That's the card. If a number you were expecting is missing, it is missing on purpose: it has not yet been traced to a source we can stand behind, and until it is, the site teaches the concept without it.
References
- Mayo-Smith WW, Song JH, Boland GL, et al. Management of Incidental Adrenal Masses: A White Paper of the ACR Incidental Findings Committee. J Am Coll Radiol 2017;14(8):1038–1044. Used for: in "Adrenal": the ≤10 HU unenhanced threshold, the ≥60% absolute and ≥40% relative washout cutoffs and their formulas, the adrenal-protocol CT timing (60–90 s dynamic phase, 15-min delay, 3 mm collimation, 120 kVp), the <10 HU change definition of a non-enhancing mass, the macroscopic-fat and chemical-shift benign features, the 1 to <4 cm and >10 HU indication for adrenal-protocol CT, the ≥4 cm resection recommendation, the absence of a growth-rate threshold, and the central-necrosis rule.
- Caoili EM, Korobkin M, Francis IR, et al. Adrenal masses: characterization with combined unenhanced and delayed enhanced CT. Radiology 2002;222(3):629–633. Used for: in "Adrenal": the ≤10 HU and ≥60% washout thresholds as used in the combined CT series, and the 166-mass (127 adenomas, 39 non-adenomas) accuracy row.
- Boland GW, Lee MJ, Gazelle GS, Halpern EF, McNicholas MM, Mueller PR. Characterization of adrenal masses using unenhanced CT: an analysis of the CT literature. AJR Am J Roentgenol 1998;171(1):201–204. Used for: in "Adrenal": the sensitivity and specificity ranges across 2 HU to 20 HU thresholds (47% to 88% sensitivity; 100% to 84% specificity) from 10 reports and 495 lesions, and the ≤10 HU threshold row.
- Israel GM, Korobkin M, Wang C, Hecht EN, Krinsky GA. Comparison of unenhanced CT and chemical shift MRI in evaluating lipid-rich adrenal adenomas. AJR Am J Roentgenol 2004;183(1):215–219. Used for: in "Adrenal": the chemical-shift MRI signal-loss sign of a lipid-rich adenoma.
- Herts BR, Silverman SG, Hindman NM, et al. Management of the Incidental Renal Mass on CT: A White Paper of the ACR Incidental Findings Committee. J Am Coll Radiol 2018;15(2):264–273. Used for: in "Renal mass attenuation and enhancement": the < −10 HU fat threshold, the −10 to +20 HU simple-cyst definition, the ≥70 HU hyperdense-cyst rule, the >20 and <70 HU indeterminate band, the too-small-to-characterize definition and the <1.5 cm MRI preference, the benign-by-size percentages (≈40%, ≈20%, <10%), the stability definition (≤3 mm per year for at least 5 years; growth ≥4 mm per year), and the AML ≥4 cm and aneurysm >0.5 cm referral thresholds.
- Silverman SG, Pedrosa I, Ellis JH, et al. Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment. Radiology 2019;292(2):475–488. Used for: in "Bosniak v2019": every class definition (I, II, IIF, III, IV) with their 2 mm, 3 mm, and 4 mm wall and septal thresholds, the −9 to 20 HU, 21–30 HU, and ≥70 HU attenuation bands, and the summarized malignancy likelihoods; also the Bosniak I and II labels in "Renal mass attenuation and enhancement."
- Oesterling JE, Fishman EK, Goldman SM, Marshall FF. The management of renal angiomyolipoma. J Urol 1986;135(6):1121–1124. Used for: in "Renal mass attenuation and enhancement": the origin of the 4 cm angiomyolipoma treatment cutoff.
- Amin MB, Edge SB, Greene FL, et al., eds. AJCC Cancer Staging Manual. 8th ed. Springer; 2017. Kidney chapter (renal cell carcinoma TNM). Used for: in "RCC staging": the T1a to T4 definitions including the 4 cm, 7 cm, and 10 cm size cutoffs.
- Smith RC, Verga M, McCarthy S, Rosenfield AT. Diagnosis of acute flank pain: value of unenhanced helical CT. AJR Am J Roentgenol 1996;166(1):97–101. Used for: in "Urolithiasis": the 97% sensitivity, 96% specificity, and 97% accuracy of unenhanced helical CT for ureteral stones.
- Preminger GM, Tiselius HG, Assimos DG, et al. 2007 Guideline for the management of ureteral calculi. J Urol 2007;178(6):2418–2434. Used for: in "Urolithiasis": the spontaneous passage rates of 68% (95% CI 46–85%) for stones ≤5 mm and 47% for >5 to ≤10 mm, from 224 and 104 patients.
- Coll DM, Varanelli MJ, Smith RC. Relationship of spontaneous passage of ureteral calculi to stone size and location as revealed by unenhanced helical CT. AJR Am J Roentgenol 2002;178(1):101–103. Used for: in "Urolithiasis": the passage rates by CT-measured size (1 mm 87%; 2–4 mm 76%; 5–7 mm 60%; 7–9 mm 48%; >9 mm 25%) and by location (proximal 48%, mid 60%, distal 75%, ureterovesical junction 79%).
- Chlapoutakis K, Theocharopoulos N, Yarmenitis S, Damilakis J. Performance of computed tomographic urography in diagnosis of upper urinary tract urothelial carcinoma, in patients presenting with hematuria: Systematic review and meta-analysis. Eur J Radiol 2010;73(2):334–338. Used for: in "CT urography": the pooled sensitivity of 96% (95% CI 88–100%) and specificity of 99% (95% CI 98–100%).
- Van Der Molen AJ, Cowan NC, Mueller-Lisse UG, Nolte-Ernsting CC, Takahashi S, Cohan RH; CT Urography Working Group of the European Society of Urogenital Radiology (ESUR). CT urography: definition, indications and techniques. A guideline for clinical practice. Eur Radiol 2008;18(1):4–17. Used for: in "CT urography": the split-bolus versus single-bolus phase strategies and the CTDIvol dose bands (5–6 mGy, 9–12 mGy, and 2–3 mGy for the optional unenhanced series).
- Panebianco V, Narumi Y, Altun E, et al. Multiparametric Magnetic Resonance Imaging for Bladder Cancer: Development of VI-RADS (Vesical Imaging-Reporting And Data System). Eur Urol 2018;74(3):294–306. Used for: in "VI-RADS": the category 1 to 5 definitions including the 1 cm size split, and the dominant-sequence rule (DWI, then DCE if DWI is suboptimal).
- Huang JJ, Tseng CC. Emphysematous pyelonephritis: clinicoradiological classification, management, prognosis, and pathogenesis. Arch Intern Med 2000;160(6):797–805. Used for: in "Renal infection": the class 1, 2, 3A, 3B, and 4 definitions of emphysematous pyelonephritis and the prognosis note.
- House MK, Dowling RJ, King P, Gibson RN. Using Doppler sonography to reveal renal artery stenosis: an evaluation of optimal imaging parameters. AJR Am J Roentgenol 1999;173(3):761–765. Used for: in "Renal vascular and transplant": the peak systolic velocity 180 cm/s and renal–aortic ratio 3.0 thresholds and their combined sensitivity 85% and specificity 76%.
- Naesens M, Heylen L, Lerut E, et al. Intrarenal resistive index after renal transplantation. N Engl J Med 2013;369(19):1797–1806. Used for: in "Renal vascular and transplant": the ≥0.80 allograft resistive index threshold, its formula, and its association with recipient mortality rather than graft outcome.
- Emamian SA, Nielsen MB, Pedersen JF, Ytte L. Kidney dimensions at sonography: correlation with age, sex, and habitus in 665 adult volunteers. AJR Am J Roentgenol 1993;160(1):83–86. Used for: in "Renal vascular and transplant": the median kidney lengths (11.2 cm left, 10.9 cm right) and volumes (146 cm³ left, 134 cm³ right) in 665 volunteers.
- Kozar RA, Crandall M, Shanmuganathan K, et al.; AAST Patient Assessment Committee. Organ injury scaling 2018 update: Spleen, liver, and kidney. J Trauma Acute Care Surg 2018;85(6):1119–1122. Used for: in "Renal trauma (AAST 2018)": the grade I to V kidney injury definitions including the 1 cm laceration depth split, the grading rules, and the vascular injury and active bleeding definitions.
- Nguyen HT, Benson CB, Bromley B, et al. Multidisciplinary consensus on the classification of prenatal and postnatal urinary tract dilation (UTD classification system). J Pediatr Urol 2014;10(6):982–998. Used for: in "Urinary tract dilation": the antenatal APRPD thresholds (4 mm and 7 mm at 16–27 weeks; 7 mm and 10 mm at ≥28 weeks) and the postnatal UTD P1 to P3 definitions (10 mm and 15 mm APRPD).
- Fernbach SK, Maizels M, Conway JJ. Ultrasound grading of hydronephrosis: introduction to the system used by the Society for Fetal Urology. Pediatr Radiol 1993;23(6):478–480. Used for: in "Urinary tract dilation": the SFU grade 1 to 4 definitions.
- Turkbey B, Rosenkrantz AB, Haider MA, et al. Prostate Imaging Reporting and Data System Version 2.1: 2019 Update of Prostate Imaging Reporting and Data System Version 2. Eur Urol 2019;76(3):340–351. Used for: in "Prostate (PI-RADS v2.1)" and the Key Points: the categories 1 to 5, the dominant sequences, the upgrade rules, the 1.5 cm threshold between scores 4 and 5, the ≥1400 s/mm² b-value and ≤15 s DCE temporal resolution, and the ellipsoid volume formula (× 0.52).
- Woo S, Suh CH, Kim SY, Cho JY, Kim SH. Diagnostic Performance of Prostate Imaging Reporting and Data System Version 2 for Detection of Prostate Cancer: A Systematic Review and Diagnostic Meta-analysis. Eur Urol 2017;72(2):177–188. Used for: in "Prostate (PI-RADS v2.1)": the pooled sensitivity 89% and specificity 73% from 21 studies and 3857 patients.
- Lam Shin Cheung J, Bhaduri M. A sound approach to stay on the ball—a review of scrotal pathologies on ultrasound imaging. Br J Radiol 2026;99(1181):847–858. Used for: in "Scrotum" and the Key Points: the normal testis (5 × 3 × 2 cm), epididymal head (10–12 mm), tunica vaginalis fluid (2–3 mL), the varicocele cut-offs (2.5 mm at rest, 3.0 mm with Valsalva) and 97% sensitivity and 94% specificity, the whirlpool sign (92% sensitivity, 99% specificity), the epididymitis figures (70% sensitivity, 88% specificity), and the across-series rupture ranges (64–100% sensitivity, 65–93.5% specificity).
- Ota K, Fukui K, Oba K, et al. The role of ultrasound imaging in adult patients with testicular torsion: a systematic review and meta-analysis. J Med Ultrason 2019;46(3):325–334. Used for: in "Scrotum" and the Key Points: the pooled torsion figures (sensitivity 0.86, 95% CI 0.79–0.91; specificity 0.95, 0.92–0.97) and the post-2010 figures (sensitivity 0.95, 0.84–0.99; specificity 0.98, 0.93–0.99).
- Buckley JC, McAninch JW. Use of ultrasonography for the diagnosis of testicular injuries in blunt scrotal trauma. J Urol 2006;175(1):175–178. Used for: in "Scrotum": the 100% sensitivity and 93.5% specificity for testicular rupture in 65 patients.
- Richenberg J, Belfield J, Ramchandani P, et al. Testicular microlithiasis imaging and follow-up: guidelines of the ESUR scrotal imaging subcommittee. Eur Radiol 2015;25(2):323–330. Used for: in "Scrotum": the microlithiasis follow-up rules, including annual ultrasound up to age 55 with risk factors.