Kristina M. Nowitzki, M.D., Ph.D. And Hao S. Lo, M.D.

Kristina M. Nowitzki, M.D., Ph.D. and Hao S. Lo, M.D.University of Massachusetts Medical School, Worcester, MA

OutlineI.II.Introduction highlighting normal renal enhancementphysiology including normal CT nephrogram phases.Cases organized in a quiz format, with etiologiesincluding:a. obstructiveb. vascularc. traumaticd. infectious/inflammatorye. neoplasticWould you like to skip the brief introduction?Click the menu button at any point to skip/return to the case menu:

IntroductionBasics of Renal Contrast EnhancementExcreted primarily by glomerularfiltration, contrast begins to fill theIV contrast briskly enters the kidneys through therenal arteries:tubules and collecting ducts andmedullary tissue begins to enhance.Cortex glomeruli nephrons Main renal artery Interlobar arteries Arcuate arteries Cortical radiate arteriesMedulla juxtamedullarynephrons collecting ductsNormally, symmetric patterns of renal enhancementEarly in imaging, the distribution oftermed “nephrograms” can be seen in a predictablearteries and capillaries governs renaltime course after contrast administration enhancement.

IntroductionNoncontrastIVCAoCortex, Medulla: 30-40 HU

IntroductionCorticomedullaryEarly: 15-60sIVCNote arterialphase of contrastin IVC and aortaAoCortex enhances briskly as contrast fills cortical capillaries.Maximal differentiation between cortex and medullae.g. @40-50s : cortex 145-185 HU, medulla 50-90 HU

IntroductionNephrographicMid: 80-120sIVCNote venous phaseof contrast in theIVC and aortaAoContrast is filtered by glomeruli, enters loops of Henle andcollecting ducts.Homogeneous enhancement of both cortex and medulla

IntroductionExcretoryDelayed: 3-5minIVCAoContrast is excreted into the calyces.Contrast no longerseen in the IVC oraorta

IntroductionAltered NephrogramsNephrograms can be altered by problems in one of four basic categories:Blood flow inBlood flow outNephron FunctionUrine outflowExamples of each of these will be outlined in the specific cases that follow.

Case 1Case 5Case 9Case 13Case 2Case 6Case 10Case 14Case 3Case 7Case 11Case 4Case 8Case 12

33 year old presents after MVAName that nephrogram:Case 1Absent NephrogramMost likely diagnosis:Right renal artery transectionArterial phase MIP image with essentially absent nephrogramin a normal size right kidney. There is a pararenal hematoma(arrow). Abrupt cutoff of the right main renal artery near itsorigin (arrowhead) indicates total transection. A normalcorticomedullary nephrogram is seen on the left.

69 year old presents with flank painCase 2Name that nephrogram:Absent NephrogramMost likely diagnosis:Right infiltrative renal malignancyArterial phase image with absent nephrogram on theright. There is loss of the normal renal sinus fat. A normalright main renal artery is seen (arrow). Additionalsections through the lung bases and liver (not shown)showed diffuse metastatic disease. A normalcorticomedullary nephrogram is seen on the left.

69 year old presents with chest painCase 3Name that nephrogram:Absent NephrogramMost likely diagnosis:Aortic dissection involving theleft renal arteryArterial phase images with absent nephrogram on the left.There is a long segment aortic dissection (arrowheads)involving the left renal artery (arrow). A normalcorticomedullary nephrogram is seen on the right.

Cases 1-3Absent NephrogramMost commonly the result of complete arterial occlusionEspecially in blunt abdominal trauma with renal pedicle injuryNo blood in Acute, complete arterial occlusion transection (look for hematoma), dissection, thromboembolic diseaseNo blood out Acute, complete venous occlusion (less common than arterial causes) hypercoagulable state, tumor invasion, nephrotic syndromeNo nephrons Infiltrative mass (lymphoma, diffuse TCC, mets) Congenital or acquired (XGP, TB autonephrectomy)No urine out Uncommon (e.g. multicystic dysplastic kidney)

Cases 428 year old presents with flank painName that nephrogram:Most likely diagnosis:Need a hint? Click here

Cases 428 year old presents with flank painName that nephrogram:Most likely diagnosis:

Cases 428 year old presents with flank painName that nephrogram:Unilateral Delayed NephrogramMost likely diagnosis:Obstructing ureteral stoneThe venous phase of intravascular contrast indicates thatthe right nephrographic phase is normal with a delayedcorticomedullary nephrogram on the left. Mildhydronephrosis is also seen on the left (arrow). Additionalsagittal view of the bladder in the same patientdemonstrates a punctate stone in the most dependentportion of the urinary bladder, settling there after havingjust passed through the left ureter (arrowhead).

Cases 532 year old presents with abdominal pain, hematuriaName that nephrogram:Most likely diagnosis:Need a hint? Click here

Cases 532 year old presents with abdominal pain, hematuriaName that nephrogram:Most likely diagnosis:

Cases 532 year old presents with abdominal pain, hematuriaName that nephrogram:Unilateral Delayed NephrogramMost likely diagnosis:Acute renal vein thrombosisEnlarged, edematous left kidney with extremely delayedcorticomedullary nephrogram throughout. The renalarteries are opacified, but no contrast is seen within theleft renal vein. Coronal view confirms large filling defectwithin the left renal vein. External compression of the leftrenal vein by the superior mesenteric artery (Nutcrackersyndrome) was suspected.

Cases 635 year old male s/p MVAName that nephrogram:Unilateral Delayed NephrogramMost likely diagnosis:Traumatic left subcapsular hematomaand associated lacerationThere is a delayed nephrogram on the left with a smallsubcapsular hematoma (arrow). Irregularity of the leftposterior cortex is consistent with laceration.

73 year old on rivaroxaban with acute flank painCases 7Name that nephrogram:Unilateral Delayed NephrogramMost likely diagnosis:Spontaneous subcapsular hematomaassociated with anticoagulationThere is a large subcapsular hematoma on the right with masseffect on the right kidney which demonstrates a delayedcorticomedullary nephrogram. Extravasation of IV contrast(arrow) is consistent with ongoing hemorrhage. A small cyst isalso present in the right lower pole (star).

Cases 4-7Unilateral Delayed NephrogramMost common cause is obstructive uropathySlow blood in Renal artery stenosis Subcapsular hematoma (Page kidney)Slow blood out Renal vein occlusion or compressionPoor nephronfunction Unilateral pyelonephritisSlow urine out Obstructive uropathy (e.g. stones, blood clot, tumor, lymphadenopathy)

Cases 823 year old with acute flank painName that nephrogram:Striated NephrogramMost likely diagnosis:PyelonephritisThere is a striated nephrogram on the right with radiallyoriented linear areas of poor enhancement involving bothcortex and medulla. The left kidney demonstrates anormal nephrographic phase nephrogram.

15 year old s/p MVACases 9Name that nephrogram:Bilateral Striated NephrogramMost likely diagnosis:Renal contusionsSegmental areas of delayed medullary enhancement in bothkidneys give the appearance of a patchy striatednephrogram. In the acute traumatic setting this most likelyrepresents areas of contusion. A portion of a liver lacerationis also seen (arrows).

Cases 1069 year old with dropping systolic blood pressureName that nephrogram:Bilateral Striated NephrogramMost likely diagnosis:Systemic hypotensionStriated nephorgrams are seen in both kidneys. The IVC(arrow, adjacent to the right renal artery) is markedlyflattened, consistent with severe hypotension. Perfusionabnormalities were also seen in the liver and spleen (notshown).

Cases 8-10Striated NephrogramTubular stasis by pus (pyelonephritis) or interstitial edema results in raysof low enhancement. These same areas may demonstrate increasedattenuation on delayed images due to hyperconcentration of contrast.UnilateralAcute pyelonephritisUreteric obstructionBilateralAcute pyelonephritisTubular obstruction(e.g. proteinuria, myoglobinuria)ContusionHypotensionRenal vein thrombosisAutosomal recessivepolycystic kidney disease

Cases 1182 year old with abdominal painName that nephrogram:Spotted NephrogramMost likely diagnosis:Renal infarcts from multipleemboliSpotted nephrogram in the left kidney, betterappreciated on the coronal view. An additionallesion was seen in the lower pole of the rightkidney (not shown). MIP image from the samestudy shows a small filling defect within anaccessory renal artery supplying the left upperpole (arrow).

Cases 1266 year old with abdominal painName that nephrogram:Spotted NephrogramMost likely diagnosis:Vasculitis (polyarteritis nodosa)Wedge shaped area of decreased perfusion in the lowerpole of the left kidney. A normal corticomedullarynephrogram is seen on the right. On MIP images (lower),mural thickening with abrupt narrowing of a left lower renalartery branch (left). Similar segments of mural thickeningand luminal narrowing seen in the left gastric artery (right).

Cases 11-12Spotted NephrogramIndicates segmental problems in perfusion or nephron functionBlood inPoor nephronfunction Embolic disease Intrarenal vasculitis PyelonephritisExample of a spotted nephrogramappearance in a patient with right-sidedpyelonephritis.

54 year old with rising creatinineCase 13Name that nephrogram:Bilateral Persistent NephrogramMost likely diagnosis:Acute tubular necrosis (ATN),contrast induced nephropathyThough no contrast is seen in the IVC or aorta, acorticomedullary nephrogram is present in both kidneysalong with excretion of contrast. These findings representretained contrast from a prior contrast enhanced study.

Cases 1435 year old with acute renal failure and suspicious lucent bone lesionsName that nephrogram:Bilateral Persistent (Striated)NephrogramStriated nephorgrams are seen in both kidneys on thisnoncontrast study. The hyperdense areas representhyperconcentrated retained contrast from a PE protocolchest CT performed earlier that day. The striatedappearance of the delayed nephrogram is likely related toareas of tubular obstruction from amyloid deposits orBence Jones proteins.Most likely diagnosis:Tubular obstruction frommultiple myeloma

Case 13-14Bilateral Persistent NephrogramRetention of contrast in cortex or cortex collecting tubules forgreater than 3 minutes.SystemicHypotension Look for CT findings of hypotension (flattened IVC, shock bowel, etc.)Intrarenalobstruction Acute tubular necrosis (e.g. contrast induced nephropathy, hypoxic) Mechanical intrarenal obstruction Urate crystals (e.g. tumor lysis syndrome) Protein (e.g. myoglobinuria, Bence Jones proteinuria)

SummaryAsymmetric renal enhancement is a common finding in the acutecare setting.Knowledge of the various etiologies can improve alUnilateral DelayedUreteral obstructionStriatedSpottedPersistentUreteral or tubularobstructionATN, tubularobstructionHypotensionVascularComplete arterial venous occlusionRenal artery stenosis, Renal vein thrombosis, Embolic disease,Renal vein occlusion HypotensionVasculitisTraumaticArterial culosisautonephrectomyAcute pyelonephritisAcute pyelonephritisNeoplasticInfiltrative tumorObstructing tumor/lymphadenopathyAcute pyelonephritis

ReferencesSaunders, H. S., R. B. Dyer, R. Y. Shifrin, E. S. Scharling, R. E. Bechtold, and R. J. Zagoria. “The CTNephrogram: Implications for Evaluation of Urinary Tract Disease.” Radiographics: A Review Publicationof the Radiological Society of North America, Inc 15, no. 5 (September 1995): 1069–85; discussion1086–88. doi:10.1148/radiographics.15.5.7501851.Wolin, Ely A., David S. Hartman, and J. Ryan Olson. “Nephrographic and Pyelographic Analysis of CTUrography: Principles, Patterns, and Pathophysiology.” AJR. American Journal of Roentgenology 200, no.6 (June 2013): 1210–14. doi:10.2214/AJR.12.9691.Wolin, Ely A., David S. Hartman, and J. Ryan Olson. “Nephrographic and Pyelographic Analysis of CTUrography: Differential Diagnosis.” AJR. American Journal of Roentgenology 200, no. 6 (June 2013):1197–1203. doi:10.2214/AJR.12.9692.

Unilateral Delayed Nephrogram Spontaneous subcapsular hematoma associated with anticoagulation There is a large subcapsular hematoma on the right with mass effect on the right kidney which demonstrates a delayed corticomedullary nephrogram. Extravasation of IV contrast (arrow) is consistent