< Presentation of Case >
A 69-year-old man had been otherwise well until two weeks earlier when asked for help at ER because of low-back pain and uncontrolled hypertension (170/95 mmHg) for two weeks. He had been diagnosed as having diabetes mellitus and hypertension for five years, for which he regularly received treatment with irbesartan, labetalol, simvastatin and oral hypoglycemic agents (metformin and glimepiride), respectievly. His blood pressure was usually maintained around 135/80 mmHg. The pain was gradually onset and dull in character without radiation initially. Subsequently, referred pain to supra-pubic region was noted. He denied a recent history of trauma prior to the onset of pain or recent weight loss. He also denied exposure to methysergide or asbestos. At ER, physical examination revealed a modest obese but well-developed man. Heart rate was 90 bpm, temperature was 37.0 ℃, blood pressure was 176/96 mmHg. There was no pale conjunctiva or icteric sclera. The heart beats were regular and cardiac auscultation did not show cardiac murmurs. Auscultation of the lungs was unremarkable. Abdominal exam was normal and no bruits were heard. There was no local tenderness or knocking tenderness at the back, or skin lesions at the lower back region (L3 to L5). Mild low leg edema was noted. Rectal exam did not detect asymmetric prostate enlargement. The KUB X-ray only showed degenerative changes over lumbar spine and mild scoliosis. Laboratory evaluation revealed normal electrolyte levels but mild anemia and impaired renal function (see Laboratory). Urine analysis revealed only proteinuria (see Laboratory). Because of the high blood pressure and renal failure of unknown etiology, he was admitted for further management.
< Laboratory and Image Study>
1. CBC/DC:
Day after admission |
WBC
K/μL |
Hgb
g/dL |
Hct
% |
Plt
K/μL |
Band
% |
Seg
%
|
Eos
%
|
Lym
%
|
OPD |
7.5 |
12.1 |
36.2 |
410 |
N/A
(not available) |
N/A |
N/A |
N/A |
Admission |
7.6 |
11.9 |
34.2 |
422 |
0 |
72 |
2.1 |
3.9 |
Day 3 |
7.54 |
12.0 |
35.8 |
415 |
N/A |
N/A |
N/A |
N/A |
Day 7 |
7.59 |
12.2 |
36.4 |
414 |
0 |
70 |
1.6 |
3.4 |
Day 15 |
8.01 |
12.7 |
37.4 |
434 |
0 |
75 |
1.6 |
3.1 |
Discharge |
7.67 |
12.5 |
36.6 |
420 |
N/A |
N/A |
N/A |
N/A |
2. Biochemistry:
Day after hospitalization |
BUN
mg/dl |
Cre
mg/dl |
Na
mmol/l |
K
mmol/l |
|
AST
U/l |
ALT
U/l |
Albumin
mg/dl |
T-Bil
mg/dl |
AC sugar
mg/dl |
HbA1C |
OPD |
22 |
1.5 |
141 |
4.1 |
|
36 |
32 |
3.9 |
0.8 |
88 |
6.5 |
Admission |
58 |
4.1 |
136 |
5.1 |
|
41 |
36 |
3.8 |
0.8 |
265 (random) |
N/A |
Day 3 |
49 |
3.9 |
138 |
4.2 |
N/A |
N/A |
N/A |
N/A |
N/A |
120 |
N/A |
Day 7 |
38 |
3.5 |
138 |
4.2 |
N/A |
N/A |
N/A |
N/A |
N/A |
106 |
N/A |
Day 15 |
32 |
2.1 |
137 |
4.1 |
2.32 |
N/A |
N/A |
N/A |
N/A |
98 |
N/A |
Discharge |
25 |
1.9 |
138 |
3.9 |
N/A |
36 |
N/A |
3.7 |
N/A |
100 |
N/A |
Table 3. Urine analysis
Date |
Appearance |
Specific gravity |
pH |
Protein
(mg/dl) |
Glucose |
Ketone |
Occult blood |
OPD |
yellow, clear |
1.005 |
6.5 |
50 |
-- |
-- |
-- |
On admission |
yellow, clear |
1.010 |
6.5 |
50 |
-- |
-- |
-- |
Discharge |
yellow, clear |
1.010 |
6.5 |
30 |
-- |
-- |
-- |
Date |
Urobilinogen |
Bilirubin |
RBC |
WBC |
Epithelial cells |
Cast |
Bacteria |
OPD |
0.1 |
-- |
-- |
<5 |
-- |
Granular |
-- |
On admission |
0.1 |
-- |
<5 |
<5 |
-- |
Granular |
-- |
Discharge |
0.1 |
-- |
-- |
<5 |
+ |
Granular |
-- |
4. Serology studies: CRP: 5.6 mg/dl, ESR: 60 mm/h
5. CXR and KUB X-ray: Normal lung field without space occupying lesion. No cardiomegaly. Mild degenerative change of L-spine was noted. No radiopaque lesion was noted along the ureter pathway.
6. Renal ultrasonography: Normal kidney size with mild to moderate unilateral (left) hydronephrosis and hydroureter. No tumor or hyperechoic lesion is seen, and the prostate is mildly enlarged.
7. Abdomen and pelvis MRI: A retroperitoneal soft tissue mass, 5 x 4.5 x 6 cm in size, extends from the left renal hilum to the presacral space. The left renal artery is encased by the mass. The mass extends from the aorta and encases as well as draws the left ureter medially. No lymphadenopathy is noted. The prostate is mildly enlarged. The left renal artery is partially compressed within the mass.
8. Pathology of Retroperitoneal mass: Five different specimens are obtained from different sites of the mass. The biopsy tissue is consisted mostly of fibrosis and chronic inflammation, without evidence of malignancy.
< Course and Treatment >
Upon admission, acute on chronic renal failure resulting from obstructive nephropathy was suspected and supportive treatment was initiated. Anti-hypertensive medications were adjusted. The urine output was around 1000 ml/day, and therefore, no dialysis was ever considered. Because of the unilateral hydronephrosis and hydroureter in his age, malignancy was considered. Abdomen and pelvis MRI was performed, which disclosed a retroperitoneal soft-tissue mass. A CT-guided biopsy was performed and the pathology revealed a fibrosis-predominant tissue without malignancy, which suggested retroperitoneal fibrosis. Since the left ureter was entrapped and left renal artery was partially compressed in the fibrotic mass, ureterolysis was performed and left renal artery was also freed from the compression. After surgery and supportive treatment, patient's renal function and blood pressure returned to near pre-hospitalization levels. Prednisolone 20 mg/day and mycophenolate mofetil (MMF) 1000 mg/day were begun for retroperitoneal fibrosis. Prednisolone was gradually tapered but MMF was continued. He was discharged and followed up at the outpatient clinic. No change of the tumor was noted three months later, but his renal function and blood pressure remained stable.
< Analysis >
臨床上評估腎衰竭時，不論年紀或性別，因腎後阻塞(post-renal obstruction)造成的阻塞性腎病變是一定要優先排除的。腎後阻塞可以因內在(intrinsic)和外在(extrinsic)原因引起，而出現在腎臟到尿道之間。但是在不同年紀、不同性別，會有不同的鑑別診斷。由於初期症狀不明顯，因此腎後阻塞的盛行率(prevalence)是被低估的，甚至於不同時間、不同性別會導致不同的結果。一般來說，在20歲前，男女之間的發生率(incidence)是差不多的，在一項解剖研究發現，十歲以下的兒童的阻塞多因尿道、輸尿管阻塞或因神經性疾病引起。在20至60歲間的女性，絕大多數腎後阻塞的主因是懷孕或婦科方面的癌症。而當阻塞發生在60歲之後，則主要影響男性，且以良性攝護腺肥大或攝護腺癌為主因。阻塞性腎病變的鑑別診斷請見Table 1 ~3。雖然腎後阻塞引起的腎衰竭，在解除阻塞後腎功能大多可恢復，但若阻塞的時間太久，還是會造成不可逆的腎臟傷害。腎後阻塞依發生時間可分為急性(幾小時至幾天)、亞急性(幾天至幾星期)與慢性(幾個月至幾年)。急性阻塞的症狀以突然發作的疼痛為主。若是以單側急性發作表現，約在腎盂或輸尿管路徑上時，需要考慮nephrolithiasis及papillary necrosis。若是阻塞發生在膀胱，則會以supra-pubic pain為主，並可能伴隨尿急、頻尿甚至無尿。慢性阻塞的症狀則通常並不明顯，關於亞急性阻塞的症狀則隨病因有所差異，不過亞急性與慢性阻塞是以逐漸惡化的症狀為表現。另外臨床上要考慮的還包括受阻塞影響的腎臟數目，若是兩側腎臟都受影響(或單側受影響，但只具有一顆腎臟)，一定時間後，腎臟功能相關之生化及尿液檢查都會出現異常；但若是只有一側腎臟受影響，而另一側腎臟功能基本正常，則腎臟功能相關之生化檢查可能因另側腎臟之代償而為正常，此時就只能試著從尿液檢查中去猜測病因。
在本病例中，在確定診斷之前，如前所述，由於是年紀大之男性病患，以良性攝護腺肥大或攝護腺癌為阻塞主因，但值得懷疑的是，若是因良性攝護腺肥大或攝護腺癌造成的阻塞，一般會見到兩側hydronephrosis或hydroureter，但此病患卻以單側hydronephrosis及hydroureter表現，當然攝護腺癌不是不可以以單側hydronephrosis及hydroureter表現，但針對年紀大之病患，攝護腺以外的病因影響單側腎臟或輸尿管也是要考慮。此外，不管是否為攝護腺的問題，由於此年紀屬於癌症的高危險群，因此直接以MRI檢查來幫助診斷。一方面可減少IVP (intravenous pyelogram)或CT檢查時顯影劑對此病患腎臟進一步的傷害，還可提供較IVP或RP(retrograde pyelogram)更多的資訊，如當阻塞是癌症造成時可提供癌症分期等。不過在臨床上，所有病例還是宜先以腎臟或腹部超音波檢查為篩檢的主要工具。而當MRI偵測到後腹腔腫瘤時，癌症自然是第一考慮，但是其他如感染、retroperitoneal fibrosis、post-trauma、post-radiation therapy等都要考慮。在經過病史排除、詳細檢查及切片後，確定阻塞是因retroperitoneal fibrosis造成，經過進一步手術治療後，病患腎功能逐漸恢復。
Retroperitoneal fibrosis是一種相當少見，但能造成泌尿道阻塞的疾病，發生率約每十萬人有1至2人，最常出現發生於40至60歲之間的男性，男女比為3比1。Retroperitoneal fibrosis可分為原發性及次發性，原發性常與腹部主動脈瘤有關，但原因不明，不過推測跟局部發炎有關；而次發性則與granulomatous diseases、retroperitoneal fibrosis、diverticulitis、ureteral rupture、smoking、術後沾黏、腫瘤、自體免疫疾病、石棉暴露、post-radiation therapy及某些藥物使用有關如methysergide、bromocriptine、phenacetin、ergotamines、hydralazine、methyldopa及beta-blockers。80%的病例是以非特異性且緩慢發生的背痛為主，也可能伴有發燒、倦怠及體重減輕等症狀。在此例病例中，由於retroperitoneal fibrosis造成輸尿管沾黏而引起急性腎衰竭(其實無法確定一定是急性)，及可能因壓迫到腎動脈而引起高血壓惡化。但retroperitoneal fibrosis有時也不會以泌尿腎臟症狀表現，反而沾黏壓迫如下腔靜脈而引起下肢水腫與靜脈炎或十二指腸而引起腸道阻塞等相關症狀。也有報告指出retroperitoneal fibrosis病患會有血壓升高的表現及其他不典型檢查異常如貧血、ESR(erythrocyte sedimentation rate)或CRP(C-reactive protein)的上升等。輸尿管向內側偏移是IVP檢查時可見到的典型發現，但最終診斷是需要靠病理切片。此病例因腎臟超音波發現hydronephrosis及hydroureter，由於腎功能不佳，因此藉著MRI及切片診斷出retroperitoneal fibrosis並排除惡性腫瘤。雖然病患有服用beta-blocker，但因果關係在此病例是很難確定的，所以診斷為原發性retroperitoneal fibrosis。Retroperitoneal fibrosis病理切片主要可見到fibrosis與collagen為主的發炎反應。治療主要以外科治療為主，內科治療為輔，以手術分離沾黏的輸尿管或放置ureteral stent來解除阻塞及疼痛，至於內科治療則是針對發炎現象，主要以corticosteroids為第一線用藥加上其他免疫抑制劑如azathioprine、mycophenolate和cyclophosphamide等，有些報告指出，在僅經過內科治療，retroperitoneal fibrosis是會縮小的。不過由於病例不多，因此治療藥物、劑量及療程並未標準化，不過一般治療約持續6月至12月。
< References >
- Primer on Kidney Disease, 4th Edition
- Nature Clinical Practice Nephrology 2005;1:55.
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Case Discussion
繼續教育考題