Renal And Perirenal Space Involvement In Acute Pancreatitis:an MRI Study

Objectives: To study the prevalence and characteristics of renal andperirenal space involvement and its relation to the severity of acutepancreatitis （AP） using MRI.Methods:115with AP patients performed MRI were retrospectivelyrecruited in this study. The renal and perirenal space involvement in AP wasnoted on MRI. The severity of AP on MRI was graded by MR severity index（MRSI） as mild （0-3scores）, moderate （4-6scores） and severe （7-10scores）.The relationships among the renal and perirenal space involvement on MRIand MRSI were analyzed.Results: In the115patients with AP,83%（95/115） of patients hadedematous and17%（20/115） of patients had necrotic AP on MR imaging.According to MRSI, the mild, moderate and severe AP were28%（32/115）,68%（78/115） and4%（5/115） respectively. The renal and perirenal spaceabnormalities detected included renal parenchymal abnormalities （0.8%）,abnormalities of the renal collecting system （2.6%）, renal vascularabnormalities （1.7%）, thickened renal fascia （99%）, perirenal stranding （62%）and perirenal fluid collection （40%）. The prevalence of perirenal spaceabnormalities was correlated with the severity of AP based on MRSI（P<0.05）.Conclusion: Perirenal space involvement is much more than renalparenchymal involvement in AP. The prevalence of perirenal spaceinvolvement in AP on MRI has a positive correlation with the severity of AP according to MRSI. The perirenal space involvement on MR imaging couldbe as a index for estimating and predicting the AP severity. Objective: To study the clinical application of kidney DWI in APpatients.Materials and Methods:115with AP who underwent MRI with theclinical kidney function test were retrospectively analyzed in this study. MRIsequences included conventional and diffusion weighted imaging （DWI）sequences with b value0s/mm2and500s/mm2. AP was categorized intoedematous and necrotizing according to their MR findings, and graded intomild （0-3scores）, moderate （4-6scores） and severe （7-10scores） according tothe MR severity index （MRSI）. The results of kidney function test （BUN、Crand Routine Urianlysis） were noted and compared with the severity of AP onMRSI. The renal apparent diffusion coefficient （ADC） on DWI was measuredfor each kidney. The relationships among the renal ADC, MRSI and theresults of the kidney function test were analyzed.Results: In the115AP patients,83%（95/115） of patients had edematousand17%（20/115） of patients had necrotic AP on MR imaging. According toMRSI, the mild, moderate and severe AP were28%（32/115）,68%（78/115）and4%（5/115） respectively.29%（33/115） of patients with AP had kidneyinjury, which had at least one index abnormality in kidney function test,proteinuria （30.3%） was the common type. The prevalence of the kidneyfunction abnormalities in necrotic AP patents was higher than edematous AP（55%vs23%, p=0.004）. The prevalence of kidney function abnormalities was9.4%,32%and100%in mild, moderate and severe AP cases, respectively （P=0.00）. The right and left kidney ADC values according to MRSI were2.71±0.46×10^-3mm²/s,2.66±0.49×10^-3mm²/s,2.40±0.16×10^-3mm²/s and2.48±0.41×10^-3mm²/s,2.53±0.35×10^-3mm²/s,2.19±0.21×10^-3mm²/s,respectively. The relationships of the both kidneys and MRSI had nostatistical significance, but the renal ADC values were lower in patients withabnormal kidney function than in those without kidney injury （P<0.05）.Conclusion: Kidney injury can be seen in necrotic AP more than inedematous AP, proteinuria is the most common type of kidney injury. Theabnormality of kidney function in AP was correlation with MRSI. The ADCvalue of kidney may help to predict kidney function abnormality in AP, andcould not be as a index for predicting the AP severity. Objective: To investigate the relationship between presences of delayednephrographic progression on MRI obtained within72hours of onset of APand development of acute kidney injury （AKI）.Materials and Methods: Acute pancreatitis patients performed MRenhancement scan were recruited from Jan2010to Dec2012in our institute.Triple-phase MRI protocol consisted of pancreatic and hepatic phase scanswith unenhanced scan, respectively. MRI signal intensity of renal medullawas measured on unenhanced （SI0）, pancreatic （SI1） and hepatic phases （SI2）.Relative enhancement ratio （RER） of renal medulla was calculated as （SI1–SI0）/（SI2–SI0）. Higher RER value represents poor enhancement ofmedulla in hepatic phase （delayed nephrographic progression）. The results ofkidney function test （BUN、Cr and Routine Urianlysis） were noted. Serumcreatine on admission （Cr1） and the maximum of creatine within2weeks（Cr2） were recorded. AkI was defined as Cr2/Cr1>1.5and Cr2>1.5mg/dl.Mean RERs of patients with and without AkI was compared. Spearman’scorrelation between RER and MRSI was calculated.Results: In the64AP patients performed MR enhancement scan, themild, moderate and severe AP were58%（37/64）,36%（23/64） and6%（4/64）respectively according to MRSI.25%（16/64） of patients with AP had kidneyinjury, which had at least one index abnormality in kidney function test,31%（5/16） was AKI. The right and left kidney medulla RER values according to MRSI were0.56±0.52、0.86±0.54、3.23±1.66and0.73±0.52、1.09±0.62、2.29±0.68, respectively. Spearman’s correlation coefficients between right andleft medulla RER against MRSI were r=0.671and0.891respectively（P<0.01）. RER of renal medulla in patients with ARI was significantly higherthan those without ARI （P<0.01）（right medulla:2.77±1.65vs0.49±0.35ï¼›andleft medulla:2.66±0.91vs0.61±0.49）.Conclusion: Mean RER of renal medulla was significantly higher inpatients with acute pancreatitis who later developed ARI than those who didnot. RER may be useful in predicting AKI and determining the severity of APon MRI.