Autosomal dominant polycystic kidney disease (ADPKD) is easy to diagnose and easy to under-report. Bilaterally enlarged kidneys studded with cysts, usually with liver cysts, is a diagnosis most residents make in seconds. The part that changes management is everything that comes after the diagnosis: an accurate height-adjusted total kidney volume (htTKV), the Mayo Imaging Classification (MIC) subclass derived from it, and a statement about whether the kidneys are typical or atypical. Those three items decide whether the patient is offered tolvaptan. The KDIGO 2025 ADPKD guideline is the first full international guideline on the disease, and it puts imaging at the centre of that decision [1].
This article covers the diagnostic cyst-count criteria on ultrasound and MRI, how to measure and report htTKV, the Mayo Imaging Classification, the imaging features that separate a haemorrhagic cyst from an infected one, intracranial aneurysm screening, the differential diagnosis, and a reporting template you can paste into your worklist.
What the radiologist must report in ADPKD
| Report this | How | Why it matters |
|---|---|---|
| Typical or atypical morphology | Typical = bilateral, diffuse, roughly symmetric cyst distribution. Atypical = unilateral, segmental, asymmetric, lopsided (MIC 2A) or atrophic (MIC 2B) | Only typical (class 1) kidneys can be classified. htTKV does not predict outcome in atypical disease [1][4] |
| Total kidney volume and htTKV | Segmentation on MRI or CT if available; otherwise ellipsoid equation. Divide TKV by height in metres | htTKV is the strongest prognostic biomarker in ADPKD and the input to the Mayo class [1][6] |
| Mayo Imaging Classification subclass | Plot htTKV against age (1A to 1E) | Subclass 1C to 1E defines rapidly progressive disease and tolvaptan eligibility [1][4] |
| Complicated cysts | Wall thickening, pericystic inflammation, intracystic gas, fluid-fluid levels, restricted diffusion | Separates cyst infection from cyst haemorrhage, which are managed differently [1] |
| Stones | Non-contrast CT; distinguish calculi from cyst-wall calcification | Nephrolithiasis occurs in about 20 percent and is a common cause of acute pain |
| Extrarenal findings | Liver, pancreatic, splenic and seminal vesicle cysts; hernia; aortic root calibre if visualised | Confirms the diagnosis and flags manifestations that change surgical and obstetric planning |
| A recommendation, when indicated | Screening ultrasound for at-risk first-degree relatives; TOF-MRA if the aneurysm-risk criteria are met | These are the two follow-on studies clinicians most often forget to order [1] |
ADPKD diagnostic criteria on imaging
KDIGO 2025 recommends abdominal ultrasound first for screening adults at risk of ADPKD, interpreted alongside the family history, kidney function and comorbidities (Recommendation 1.3.1, 1B). MRI, CT and genetic testing are follow-on tests that clarify an equivocal study [1].
Ultrasound criteria with a positive family history
The unified (Pei) criteria replaced the older gene-specific Ravine criteria and work whether the family mutation is PKD1, PKD2 or unknown [2]. They apply only when there is a positive family history.
| Age (years) | Criterion to diagnose | Positive predictive value | Sensitivity (unknown genotype) |
|---|---|---|---|
| 15 to 29 | 3 or more cysts, unilateral or bilateral | 100 percent | 82 percent |
| 30 to 39 | 3 or more cysts, unilateral or bilateral | 100 percent | 96 percent |
| 40 to 59 | 2 or more cysts in each kidney | 100 percent | 90 percent |
| 60 or older | 4 or more cysts in each kidney | 100 percent | 100 percent (PKD1 and PKD2) |
| Age (years) | Criterion to exclude | Negative predictive value (unknown genotype) |
|---|---|---|
| 15 to 29 | Fewer than 1 cyst | 91 percent |
| 30 to 39 | Fewer than 1 cyst | 98 percent |
| 40 to 59 | Fewer than 2 cysts in total | 100 percent |
The clinically important line is the bottom one. A normal ultrasound below age 30 does not exclude the disease, but fewer than two cysts in a 40-year-old at-risk relative does, with a negative predictive value of 100 percent. That single sentence in a report can end a family’s screening pathway.
MRI criteria, ages 16 to 40
MRI resolves cysts a few millimetres across that ultrasound misses, so the counts are different and the test performs better in young at-risk adults [3].
| Age (years) | Finding | Interpretation | Predictive value |
|---|---|---|---|
| 16 to 40 | 10 or more cysts (total, both kidneys) | Diagnostic of ADPKD | 100 percent PPV |
| 16 to 29 | Fewer than 5 cysts | Excludes ADPKD | 100 percent NPV, specificity 98.3 percent |
| 30 to 40 | Fewer than 5 cysts | Excludes ADPKD | 100 percent NPV, specificity 100 percent |
No family history
About one in four people with ADPKD has no known family history, either through a de novo variant or because the parent was never diagnosed. In that setting there are no validated cyst-count thresholds. Bilaterally enlarged kidneys with more than 10 cysts in each kidney, in the absence of features suggesting another cystic disease, is generally taken as diagnostic, and KDIGO advises that imaging plus genetic testing be used together [1]. Look actively for the discriminators listed in the differential table below, particularly renal angiomyolipomas (tuberous sclerosis), solid enhancing masses or pancreatic cysts (von Hippel-Lindau), and normal-sized or small kidneys in a dialysis patient (acquired cystic kidney disease).
Children and at-risk children
- Ultrasound is the screening modality. In a child under 15 years with a positive family history, one or more cysts is highly suspicious for ADPKD [9].
- A normal ultrasound in an at-risk child does not exclude the diagnosis, and there are no established MRI criteria below 15 years [9].
- Very-early-onset ADPKD is defined as severe disease before 18 months: antenatal hyperechogenic enlarged kidneys more than 2 SD for gestational age with oligohydramnios, or enlarged cystic kidneys with hypertension or reduced eGFR. Early-onset ADPKD is the same picture between 18 months and 15 years [1].
- KDIGO advises against routine screening for extrarenal manifestations (liver, pancreatic or splenic cysts, valvular disease, intracranial aneurysms) in children and adolescents; adult criteria apply from adulthood [1].
- A single cyst in a child with normal blood pressure, normal urinalysis, a negative family history and normal parental ultrasound is watched, not worked up [1].
Mayo Imaging Classification of ADPKD
KDIGO 2025 recommends the Mayo Imaging Classification to predict future decline in kidney function and the timing of kidney failure (Recommendation 1.4.2.1, 1B) [1]. This is the single biggest addition to what a radiologist is expected to provide, and the query most often typed by clinicians reading an ADPKD scan.
The classification first splits kidneys into typical (class 1) and atypical (class 2) morphology. Class 1 kidneys are bilateral and diffusely cystic with roughly symmetric involvement. Class 2A covers unilateral, segmental, asymmetric or lopsided disease; class 2B is the atrophic pattern, with an average kidney length under 14.5 cm and parenchyma replaced by cysts with atrophy. Only class 1 has prognostic value, and KDIGO explicitly states that people with subclass 2A and 2B should be excluded when using the MIC, because htTKV does not predict outcome in them [1][4].
Typical kidneys are then assigned a subclass by plotting htTKV against age. Each subclass corresponds to a theoretical annual htTKV growth rate, working back from an assumed 150 ml/m at birth [4].
| Subclass | Annual htTKV growth rate | Kaplan-Meier age at kidney failure | Implication |
|---|---|---|---|
| 1A | Less than 1.5 percent | Fewer than 20 percent reach kidney failure | Slow progression |
| 1B | 1.5 to 3.0 percent | 71.2 years | Slow progression |
| 1C | 3.0 to 4.5 percent | 62.8 years | Rapid progression; tolvaptan considered case by case |
| 1D | 4.5 to 6.0 percent | 55.6 years | Rapid progression |
| 1E | More than 6.0 percent | 45.1 years | Rapid progression |
The classification holds up on external validation: in an independent cohort the MIC predicted kidney failure and eGFR decline, and risk of kidney failure was 97, 92, 78 and 71 percent lower for subclasses 1A, 1B, 1C and 1D respectively than for 1E [1][5]. Two caveats belong in the report. The MIC should not be applied to people with pathogenic variants in genes other than PKD1 or PKD2, and in a young patient a small difference in htTKV shifts the class, so repeating the measurement after a year is reasonable when the value sits on a boundary [1].
The subclass can be assigned with the free Mayo Clinic ADPKD classification tool, which needs age, height and TKV.
How to measure total kidney volume and htTKV
htTKV is the sum of both kidney volumes divided by the patient’s height in metres, expressed in ml/m. Dividing by height partially corrects for body size [1].
| Method | How it works | Accuracy and caveats |
|---|---|---|
| Automated or semi-automated segmentation on MRI or CT | Software segments the whole kidney across the stack | Preferred by KDIGO for accuracy, reproducibility and speed. Needs dedicated software [1] |
| Stereology or planimetry on MRI or CT | Manual boundary tracing on every slice | Accurate reference standard but slow |
| Ellipsoid equation on MRI or CT | π/6 × length × width × depth (equivalent to L × W × D × 0.523), using sagittal and coronal measurements | Fast and acceptable, but assumes a shape that polycystic kidneys do not have, so less accurate than segmentation [1][4] |
| Ultrasound ellipsoid | Same equation on ultrasound measurements | Acceptable only when MRI and CT are unavailable or contraindicated. Underestimates TKV by about 11 percent and misassigns the Mayo class, usually to a lower one, in 22 percent of patients compared with MRI segmentation, although it still predicts high-risk subclass 1C to 1E with a positive predictive value of 98 percent [1][11] |
| Ultrasound kidney length | Mean bipolar length | A mean length above 16.5 cm predicts subclass 1C to 1E, but only in people aged 45 years or under, and it misclassifies some rapid progressors [1][12] |
Practice Point 4.1.1.2 is the one to remember at the workstation: the MIC should ideally be based on MRI, with low-dose or ultra-low-dose CT as the alternative, and ultrasound with the ellipsoid formula only when neither is available [1]. Gadolinium is not needed to measure TKV, which matters in a population with declining kidney function. Once a class is assigned, imaging in most cases can be repeated at 3 to 5 year intervals rather than annually, unless a borderline classification or a treatment decision requires it sooner [1]. Our radiology volume calculator will do the ellipsoid arithmetic for both kidneys.
Rapid progression and tolvaptan: the decision imaging drives
Tolvaptan, a vasopressin V2 receptor antagonist, is the only drug shown to slow kidney volume growth and eGFR decline in ADPKD, in TEMPO 3:4 in earlier disease and REPRISE in later disease [7][8]. KDIGO recommends initiating it in adults with an eGFR of 25 ml/min per 1.73 m2 or above who are at risk of rapidly progressive disease (Recommendation 4.1.1.1, 1B) [1].
| Requirement | Threshold |
|---|---|
| Kidney function | eGFR 25 ml/min per 1.73 m2 or above |
| AND evidence of rapid progression, by any one of | Mayo subclass 1C to 1E (1C judged case by case) Historical eGFR decline of 3 ml/min per 1.73 m2 per year or more PROPKD score above 6 |
The corollary matters for older articles and older reports: KDIGO 2025 recommends against mTOR inhibitors (sirolimus, everolimus), statins and metformin for slowing progression, and against somatostatin analogues for the sole purpose of preserving kidney function [1]. Somatostatin analogues retain a role in reducing liver volume in severely symptomatic polycystic liver disease. Water intake of at least 2 litres a day, spread through the day, is suggested, with a target morning urine osmolality below 280 mOsm/kg [1].
Cyst haemorrhage versus cyst infection
Most acute presentations in ADPKD are pain, haematuria, stones, cyst haemorrhage or cyst infection, and the last two are the hard pair. KDIGO defines likely kidney cyst infection as fever above 38 °C, acute abdominal or flank pain, and a CRP of 50 mg/l or more or a white cell count above 11 × 109/l, with at least two positive items drawn from at least two of the clinical, microbiological and imaging categories [1].
| Feature | Cyst haemorrhage | Cyst infection |
|---|---|---|
| Attenuation and signal | High attenuation on non-contrast CT; T1 hyperintense, variable T2, often a fluid-fluid level from layering blood | Complex fluid, may be indistinguishable from blood on attenuation alone |
| Cyst wall | May thicken over time; no pericystic stranding | Thickened wall, wall enhancement on CT or MRI |
| Surrounding fat | Usually clean, though acute bleeding can incite perinephric inflammation | Pericystic inflammation on CT or MRI |
| Gas | Absent | Intracystic gas is specific when present |
| Diffusion | Variable | Restricted diffusion, increased density relative to other cysts |
| Interval change | Regresses over weeks | A new complex cyst compared with imaging before symptom onset |
| Problem solving | Not usually needed | 18F-FDG PET-CT when confirmation is required; nuclear options include gallium-67 SPECT and indium-111 labelled leucocyte scans |
Two points for the report. First, no single imaging feature is diagnostic, which is why the KDIGO algorithm counts items across categories rather than relying on the scan; say what you see and let the clinical and microbiological items complete the picture. Second, comparison with any prior imaging is disproportionately valuable here, since a cyst that is new or newly complex carries more weight than any single feature on the current study. Confirmed cyst infection is treated with 4 to 6 weeks of a lipid-soluble antibiotic such as a fluoroquinolone or trimethoprim-sulfamethoxazole rather than a shorter course [1].
Renal cell carcinoma in ADPKD
KDIGO 2025 states there is no clear association between ADPKD and an increased risk of renal cell carcinoma, so surveillance imaging for cancer is not indicated [1]. The practical warning is different: when RCC does occur in ADPKD it presents atypically, and a solid or thick enhancing nodular component against a background of hundreds of cysts is easy to overlook. Look at the enhancing tissue, not just the cysts, and compare with priors.
Extrarenal manifestations and intracranial aneurysm screening
ADPKD behaves like a disorder of wall integrity, which is a useful way to remember the extrarenal list: cysts in other epithelial organs, aneurysms in arteries, hernias in the abdominal wall, diverticulosis in the colon.
| Manifestation | Imaging note |
|---|---|
| Polycystic liver disease | The commonest extrarenal finding, more severe in women. Report liver volume when the burden is symptomatic, since somatostatin analogues are an option in severe symptomatic disease [1] |
| Pancreatic, splenic, seminal vesicle, arachnoid cysts | Supportive of the diagnosis; no surveillance needed |
| Intracranial aneurysm | Prevalence 12.9 percent versus 2.9 percent in the general population, rising to 17.1 percent with a family history of aneurysm or subarachnoid haemorrhage. Absolute rupture rate remains low at 0.57 per 1000 person-years [1] |
| Aortic root dilatation, thoracic aortic aneurysm, aortic dissection | KDIGO advises against routine screening of non-intracranial arteries unless there is a family history of aneurysm or dissection [1] |
| Cardiac valve disease | Echocardiography if there is a murmur, severe or uncontrolled hypertension, or a family history of thoracic aortic aneurysm [1] |
| Abdominal wall and inguinal hernia | Common with large kidneys or liver; relevant before peritoneal dialysis [1] |
| Colonic diverticulosis | Incidental, no specific action |
Aneurysm screening is targeted, not universal. KDIGO recommends screening people with ADPKD who have a personal history of subarachnoid haemorrhage or a family history of intracranial aneurysm, subarachnoid haemorrhage or unexplained sudden death, provided they would be eligible for treatment and have a reasonable life expectancy (Recommendation 6.1.2, 1D) [1]. Screening is also discussed for de novo disease, an unknown or small family, a personal or family history of extracerebral vascular disease, before kidney or liver transplantation, before major elective surgery, and before pregnancy in women in those risk groups.
- Technique: time-of-flight MR angiography without gadolinium is the method of choice; high-resolution CT angiography is the alternative [1].
- Negative screen in a high-risk person: individualised rescreening, possibly every 5 to 10 years, based on risk factors, age and life expectancy [1].
- Positive screen: management decisions belong in a multidisciplinary setting at a high-volume centre. Small anterior circulation aneurysms of 5 mm or less usually warrant surveillance rather than intervention [1].
Differential diagnosis of ADPKD
| Entity | Discriminating imaging features |
|---|---|
| ARPKD | Infants and children; symmetrically enlarged echogenic kidneys with poorly resolved microcysts and loss of corticomedullary differentiation; congenital hepatic fibrosis rather than macroscopic liver cysts |
| Acquired cystic kidney disease | Long-standing CKD or dialysis; kidneys small or normal in size, not enlarged; genuine increased risk of RCC, unlike ADPKD |
| Tuberous sclerosis complex | Fat-containing angiomyolipomas alongside cysts; cortical tubers, subependymal nodules, lymphangioleiomyomatosis. The PKD1/TSC2 contiguous gene syndrome produces severe infantile polycystic kidneys |
| Von Hippel-Lindau syndrome | Renal and pancreatic cysts plus solid enhancing lesions: clear cell RCC, haemangioblastoma, phaeochromocytoma, pancreatic neuroendocrine tumour |
| HNF1B-related disease | Small kidneys with few cysts, hyperechogenic in the fetus, often with pancreatic hypoplasia, genital tract anomalies and early-onset diabetes |
| Nephronophthisis | Normal or small echogenic kidneys with corticomedullary cysts and loss of corticomedullary differentiation; childhood or young adult CKD |
| Localised (segmental) cystic disease | Non-progressive cysts confined to one part of one kidney, with intervening normal parenchyma; normal contralateral kidney; no family history |
| Medullary sponge kidney | Ectatic papillary collecting ducts with medullary nephrocalcinosis, a brush-like blush on urography; kidneys not enlarged |
| Multiple simple cysts | Cyst number below the age-specific criteria; kidneys of normal size and shape; prevalence rises with age |
| Multicystic dysplastic kidney | Unilateral, non-communicating cysts of varying size with no functioning parenchyma; the kidney involutes over time |
ADPKD reporting template
A usable structured impression for a CT or MRI performed for known or suspected ADPKD:
- Findings: both kidneys are enlarged and diffusely replaced by innumerable cysts, in a typical (class 1) / atypical (class 2A or 2B) distribution.
- Volumes: right kidney __ ml, left kidney __ ml, total kidney volume __ ml, height __ m, htTKV __ ml/m (method: segmentation / ellipsoid).
- Mayo Imaging Classification: subclass 1A to 1E for age __ years. (Omit and state why for atypical morphology.)
- Complicated cysts: present or absent; if present, describe wall thickening, enhancement, pericystic inflammation, gas, fluid-fluid level, diffusion restriction, and compare with priors.
- Stones: present or absent; distinguish from cyst-wall calcification.
- Extrarenal: hepatic, pancreatic, splenic cysts; hernia; aortic calibre.
- Impression and recommendation: ADPKD, Mayo subclass __, in the rapid-progression range or not. Suggest screening ultrasound for first-degree relatives. Suggest TOF-MRA if aneurysm risk criteria are met.
Frequently asked questions
Key points
- Ultrasound is the first-line screening test in at-risk adults; the unified age-specific cyst counts diagnose and, above 40 years, confidently exclude the disease [1][2].
- State whether the morphology is typical or atypical before quoting any volume, because the Mayo classification is invalid in atypical kidneys [1][4].
- Report htTKV and the Mayo subclass. Subclass 1C to 1E plus an eGFR of 25 or above is what makes a patient eligible for tolvaptan [1].
- Prefer MRI or CT segmentation for volume; ultrasound underestimates and misclassifies [1][11].
- Offer screening ultrasound to first-degree relatives, and reserve TOF-MRA for the targeted aneurysm risk groups [1].
Related on RadioGyan
- Radiology volume calculator for ellipsoid organ volumes, including both kidneys.
- Normal radiology measurements reference.
- Bosniak classification calculator for the isolated complex renal cyst.
- Radiological anatomy modules and radiology spotters.
References
- Torres VE, Ahn C, Barten TRM, et al. KDIGO 2025 clinical practice guideline for the evaluation, management, and treatment of autosomal dominant polycystic kidney disease (ADPKD): executive summary. Kidney Int. 2025;107(2):234-254. PMID 39848746.
- Pei Y, Obaji J, Dupuis A, et al. Unified criteria for ultrasonographic diagnosis of ADPKD. J Am Soc Nephrol. 2009;20(1):205-212. PMID 18945943.
- Pei Y, Hwang YH, Conklin J, et al. Imaging-based diagnosis of autosomal dominant polycystic kidney disease. J Am Soc Nephrol. 2015;26(3):746-753. PMID 25074509.
- Irazabal MV, Rangel LJ, Bergstralh EJ, et al. Imaging classification of autosomal dominant polycystic kidney disease: a simple model for selecting patients for clinical trials. J Am Soc Nephrol. 2015;26(1):160-172. PMID 24904092.
- Bais T, Geertsema P, Knol MGE, et al. Validation of the Mayo Imaging Classification System for Predicting Kidney Outcomes in ADPKD. Clin J Am Soc Nephrol. 2024;19(5):591-601. PMID 38407866.
- Chapman AB, Bost JE, Torres VE, et al. Kidney volume and functional outcomes in autosomal dominant polycystic kidney disease. Clin J Am Soc Nephrol. 2012;7(3):479-486. PMID 22344503.
- Torres VE, Chapman AB, Devuyst O, et al. Tolvaptan in patients with autosomal dominant polycystic kidney disease (TEMPO 3:4). N Engl J Med. 2012;367(25):2407-2418. PMID 23121377.
- Torres VE, Chapman AB, Devuyst O, et al. Tolvaptan in later-stage autosomal dominant polycystic kidney disease (REPRISE). N Engl J Med. 2017;377(20):1930-1942. PMID 29105594.
- Gimpel C, Bergmann C, Bockenhauer D, et al. International consensus statement on the diagnosis and management of autosomal dominant polycystic kidney disease in children and young people. Nat Rev Nephrol. 2019;15(11):713-726. PMID 31118499.
- Odedra D, Sabongui S, Khalili K, et al. Autosomal dominant polycystic kidney disease: role of imaging in diagnosis and management. RadioGraphics. 2023;43(1):e220126. PMID 36459494.
- Akbari P, Nasri F, Deng SX, et al. Total kidney volume measurements in ADPKD by 3D and ellipsoid ultrasound in comparison with magnetic resonance imaging. Clin J Am Soc Nephrol. 2022;17(6):827-834. PMID 35383043.
- Bhutani H, Smith V, Rahbari-Oskoui F, et al. A comparison of ultrasound and magnetic resonance imaging shows that kidney length predicts chronic kidney disease in autosomal dominant polycystic kidney disease. Kidney Int. 2015;88(1):146-151. PMID 25830764.
Proof checked by Dr. Iranna M Hittalamani. Reviewed and updated against the KDIGO 2025 ADPKD guideline in September 2026.
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