Kidney Stone Detection on CT

Purpose	To detect kidney, ureteral, or bladder stones on CT
Tag(s)
Panel	Abdominal
Define-AI ID	20020006
Originator	Luther B. Adair, II
Lead	Luther B. Adair, II
Panel Chair	Arun Krishnaraj
Panel Reviewers	Abdominal Panel
License	Creative Commons 4.0
Status	Public Comment
RadElement Set	RDES157

Clinical Implementation

Value Proposition

Ureterolithiasis and nephrolithiasis, collectively known as kidney stones, are debilitating illnesses and common causes of emergency visits. AI meeting this use case would help in detecting, quantitating, comparing, and alerting both nonspecialists and radiologists to these abnormalities. In clinical settings where a radiologist is not readily available, such detection would be of value to non-radiologists such as technologists who would perform a CT for this disease entity. In clinical settings where radiologists are available, such detection could be used to alert the radiologist and prioritize its reporting and notification to the treating physicians.

Narrative(s)

A 28-year old patient presents to an emergency room with radiating left flank pain at which time a CT scan is ordered.

Workflow Description

The relevant images are obtained from the modality and sent to PACS and the AI engine based on anatomic landmarks. The images are analyzed by the engine. The system then detects the relevant outputs providing associated categorical data or measurements. An alert message is sent it back to the engine with information, identification, and graphics highlighting the presence of a renal calcification, ureteral calcification, urinary bladder calcification, hydronephrosis, hydroureter, perinephric collection, or whether air is present in the anatomic region of concern.

An algorithm evaluates the CT scan and assesses whether renal calculi are present, absent, or undetermined. If present, it then counts the number of calculi in each kidney and measures the largest on each side. It also assesses whether a ureteral calculus is present, absent, or undetermined. If present, it then measures the maximal size of the calcification. Assesses whether a bladder calculus is present, absent, or undetermined. If present, it then measures the maximal size of the calcification. Assesses whether hydronephrosis is present, absent, or undetermined. The algorithm assesses whether hydroureter is present, absent, or undetermined and which side. Assesses whether a perinephric collection is present, absent, or undetermined and which side. The algorithm assesses whether air is present in the urinary tract, not present, or undetermined. For cases returned where the algorithm returns air is present within the region of concern or undetermined, hydronephrosis is present or undetermined, or if there is a stone in the ureter measuring greater than 5 mm, the exam is prioritized in the radiologist’s worklist for urgent interpretation and reporting.

Considerations for Dataset Development

Procedures	{CT Abdomen, CT Abdomen and pelvis, with contrast, without contrast}
View(s)	{sagittal, axial, coronal}
Age	[0,90]
Sex at Birth	{Male, Female}
Abdominal pain	{left flank pain, right flank pain}
Other	{hydroureter, hydronephrosis, perinephric fluid collection, air within the region of concern, bladder stone}
Confounding variables	{vascular calcifications (i.e. abdominal and pelvic phleboliths) , percutaneous nephrostomy, ureteral catheter, excreted contrast, soft tissue mass anywhere in the urinary tract with or without calcifications, clot/hemorrhage in the ureter or bladder, congenital anomalies (e.g. horseshoe kidney, cross-fused ectopia, ureteral duplications, ectopic ureters, ureterocele, etc), any prior urinary tract surgery and resulting altered anatomy (e.g. nephrectomy, partial nephrectomy, ileal conduit, neobladder, etc), metallic streak artifact (e.g. lumbar fusion)}

Technical Specifications

Inputs

DICOM Study

Procedure	CT Abdomen with contrast, CT Abdomen without contrast, CT Abdomen and Pelvis with contrast, CT Abdomen and Pelvis without contrast, CT Urography, CT Pelvis
Views	Axial, coronal, and sagittal
Data Type	DICOM
Modality	CT
Body Region	Abdomen and pelvis
Anatomic Focus	Kidneys, ureters, urinary bladder

Primary Outputs

Renal Caculi Detection

RadElement ID	RDE1093
Definition	Detection of renal calcification
Data Type	Categorical
Value Set	Absent Present Indeterminate
Units	N/A

Number of Renal Caculi

RadElement ID	RDE1089
Definition	If renal caculi present, express the number of calculi present
Data Type	Numeric
Value Set	N/A
Units	N/A

Renal Calcification Measurement

RadElement ID	RDE1090
Definition	Measurement of renal calcification
Data Type	Numeric
Value Set	N/A
Units	millimeters

Ureteral Calcification Detection

RadElement ID	RDE1094
Definition	Detection of ureteral calcification
Data Type	Categorical
Value Set	Absent Present Indeterminate
Units	N/A

Ureteral Calcification Measurement

RadElement ID	RDE1091
Definition	Measurement of ureteral calcification
Data Type	Numeric
Value Set	N/A
Units	millimeters

Bladder Calcification Detection

RadElement ID	RDE1095
Definition	Detection of bladder calcification
Data Type	Categorical
Value Set	Absent Present Indeterminate
Units	N/A

Bladder Calcification Measurement

RadElement ID	RDE1092
Definition	Measurement of bladder calcification
Data Type	Measurement
Value Set	N/A
Units	millimeters

Secondary Outputs

Hydronephrosis Detection

RadElement ID	RDE1096
Definition	Detection of hydronephrosis as a function of laterality
Data Type	Categorical
Value Set	Absent Present Unknown
Units	N/A

Hydronephrosis Kidney Laterality

RadElement ID	RDE1097
Definition	If Hydronephrosis is present, identify which kidney demonstrates this feature
Data Type	Categorical
Value Set	Left Right Unknown
Units	N/A

Hydroureter Detection

RadElement ID	RDE1098
Definition	Detection of hydroureter as a function of laterality
Data Type	Categorical
Value Set	Absent Present Unknown
Units	N/A

Hydroureter Kidney Laterality

RadElement ID	RDE1099
Definition	If Hydroureter is present,identify which kidney demonstrates this feature
Data Type	Categorical
Value Set	Left Right Unknown
Units	N/A

Perinephric Fluid Detection

RadElement ID	RDE1100
Definition	Detection of perinephric fluid as a function of laterality
Data Type	Categorical
Value Set	Absent Present Unknown
Units	N/A

Perinephric Fluid Kidney Laterality

RadElement ID	RDE1101
Definition	If perinephric fluid is present, identify which kidney demonstrates this feature
Data Type	Categorical
Value Set	Left Right Unknown
Units	N/A

Air in the Urinary Tract

RadElement ID	RDE1102
Definition	Detection of air anywhere in the urinary tract
Data Type	Categorical
Value Set	Absent Present Unknown
Units	N/A

Future Development Ideas

In the case of renal calculus, the type of calculus could be further characterized by noting the density of the stone in Hounsfield units. Future consideration for characterizing hydronephrosis as mild, moderate, and severe based on how specific the algorithm can identify the value of hydronephrosis and distinguish this stratification.
One possible extension to this use case is to detect nephrolithiasis and ureteral lithiasis on CT and assess the need for further treatment based on the absence or presence of complications.

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