Renal Collecting System Calcified Hematoma Following Parenchymal Perforation by Ureteral Stent in Kidney Transplantation: A Case Report

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors reported a rare case of parenchymal perforation due to a ureteral stent after kidney transplantation. Bleeding due to parenchymal perforation was a terrible complication, leading to urinary tract obstruction and DGF early after transplantation, and severe infection one year later. Although this report is valuable, there are several points that need to be confirmed. Please refer to the points below and revise the article.

1. This case is a living donor kidney transplant, but there is little information about the donor. Kidney was damaged by catheter; thus, it is required to state whether the marginal factors such as older age that may suggest tissue fragility was present or not.

2. Some facilities add antiplatelet drugs or anticoagulants to kidney transplant protocols. Does your facility use these drugs? Or was there any special condition in which the recipient was using these drugs due to a medical history?

3. On the first day after transplant, the patient urinates more than 3L. Despite this situation, Cre level was high. Was the excessive urine caused by bleeding? Did the data show that hemoglobin was developing?

4. The authors suspected obstruction due to debris in the renal pelvis and removed the ureteral stent. Although urine outflow improved afterwards, the hematoma remained. When considering the removal of a hematoma, one possible method is to place a single-J stent and flush it. Have the authors considered this treatment? 

5. A calcified hematoma was identified one year after kidney transplant, and the patient subsequently developed emphysematous nephritis and sepsis. Infection is one cause of calcification, but did the patient have any other urinary tract infections during the first year after kidney transplant?

 6. It is stated that residual hematoma may calcify, and the cause of this formation is the same as that of urinary stones. From this perspective, it seems preferable to remove hematomas in the urinary tract, especially in patients with these risk factors (e.g. patients with recurrent urinary tract infections, metabolic disorders, etc.). Please state the authors' opinions on this point.

Author Response

Reviewer 1,

Thank you for taking the time to provide a thoughtful and comprehensive review of the manuscript. Your comments prompted several interesting discussion points that were either not included or not previously considered. The manuscript was edited accordingly and responses to your points are listed below. Of note, the other reviewers recommended decreasing the length of the manuscript. While we addressed all of your excellent points, we were limited in the extent of the edits.

Comment 1: This case is a living donor kidney transplant, but there is little information about the donor. Kidney was damaged by catheter; thus, it is required to state whether the marginal factors such as older age that may suggest tissue fragility was present or not.

Response 1: We agree that donor age and comorbidities could affect the renal parenchymal integrity. As such, we included the sentence "The kidney graft was donated by a healthy quadragenarian." (page 2, line 44-45). The donor was medically screened and cleared as an organ donor. We feel this sentence provides enough insight regarding the health of the donor without compromising any patient health information. 

Comment 2: Some facilities add antiplatelet drugs or anticoagulants to kidney transplant protocols. Does your facility use these drugs? Or was there any special condition in which the recipient was using these drugs due to a medical history?

Response 2: This comment brings up an important topic to address regarding medication exacerbating bleeding. This patient was not on anticoagulation or antiplatelets prior to surgery. They are typically started on both post-operatively, but these were held in the setting of hematuria (besides 1 dose of aspirin). We agree that this is important to address and therefore it was included in the case presentation section. "The patient did not receive anticoagulation pre- or post-operatively. However, he did receive a single low-dose aspirin on post-operative day 1, which was stopped thereafter due to persistent hematuria." (page 2, line 50-53).

Comment 3: On the first day after transplant, the patient urinates more than 3L. Despite this situation, Cre level was high. Was the excessive urine caused by bleeding? Did the data show that hemoglobin was developing?

Response 3: We are unsure why the patient had excellent urine output despite the abnormal renal function labs. It is unlikely that the bleeding accounted for this degree urine output given the relatively low decrease in hemoglobin. These values are now included based on your relevant point. "Hemoglobin measured 10.6 gm/dL (pre-operatively 11.0 gm/dL)..." & "Hemoglobin decreased to 9.6 gm/dL..." (page 2, lines 48-49 and 54). However, the decreased urine output in subsequent days could be attributed to the collecting system obstruction. 

Comment 4: The authors suspected obstruction due to debris in the renal pelvis and removed the ureteral stent. Although urine outflow improved afterwards, the hematoma remained. When considering the removal of a hematoma, one possible method is to place a single-J stent and flush it. Have the authors considered this treatment? 

Response 4: The hematoma remained, but this was not identified until future imaging. At that point, a ureteroscopy was attempted but the neo-ureteral orifice was unable to be cannulated. Immediately after the stent removal during the initial admission, the hematuria resolved and the renal function also improved so no additional intervention was performed, as we considered a nephrostomy tube as a potential next step. We did not consider the possibility of a single-J catheter for flushing, but this is a great idea so I included this as an option in the manuscript. Thank you for the excellent suggestion. "A nephrostomy tube and its associated risks of bleeding and kidney damage were avoided at that time. Exchanging the stent for a single-J catheter to allow for flushing is a feasible option, but it was not considered at the time due to prompt drainage of blood sediment during stent manipulation and removal." (page 7, lines 187-190).

Comment 5: A calcified hematoma was identified one year after kidney transplant, and the patient subsequently developed emphysematous nephritis and sepsis. Infection is one cause of calcification, but did the patient have any other urinary tract infections during the first year after kidney transplant?

Response 5: Yes - the patient experienced 3 additional, though less severe, urinary tract infections that were treated with oral antibiotics. The latter two infections were with a urease-producing organism, which likely contributed to the stone formation that was identified on ultrasound later in the patient's post-operative course. This excellent point prompted us to include the following information in the manuscript. "However, the patient experienced 3 urinary tract infections during this time: the first Escherichia coli and the latter two Klebsiella pneumoniae." (page 3, lines 89-91) and "Additionally, recurrent infections with urease-producing organisms increased the risk for infectious stone formation." (page 7, lines 199-200).

Comment 6: It is stated that residual hematoma may calcify, and the cause of this formation is the same as that of urinary stones. From this perspective, it seems preferable to remove hematomas in the urinary tract, especially in patients with these risk factors (e.g. patients with recurrent urinary tract infections, metabolic disorders, etc.). Please state the authors' opinions on this point.

Response 6: The manuscript highlights the complexity of collecting system hematomas and the potential sequelae. While it is difficult to make a definitive statement with an n=1, we agree that is important to provide an opinion on the management. Therefore, we included the following opinion at the end of the discussion section: "Removal of collecting system hematomas should be considered if its presence is prolonged and compromises the renal allograft." (page 8, lines 215-217).

Reviewer 2 Report

Comments and Suggestions for Authors

In this study, the authors reported a unique case of renal parenchymal perforation by a ureteral stent during kidney transplantation resulting in a pelvicalyceal hematoma with subsequent calcification and obstruction.

This article is original. But there are minor problems.

Minor problems

1)     I think the authors' case report is a bit too long. It should be reported more concisely.

2)     In such cases, I believe that bleeding from the edge of the ureteral stent may be observed during the procedure, so please also describe what actually occurred.

Author Response

Reviewer 2,

Thank you for taking the time to provide feedback of the manuscript. The manuscript was edited accordingly and responses to your points are listed below. 

Comment 1: I think the authors' case report is a bit too long. It should be reported more concisely.

Response 1: We agree that the case report was long and could be reported more concisely. We aimed to reduce the length of the manuscript, while maintaining the relevant content and also addressing comments made by other reviewers. Your comments prompted a critical edit of the manuscript, resulting in reduction of the Case Presentation section from 917 words to 756 words. 

Comment 2: In such cases, I believe that bleeding from the edge of the ureteral stent may be observed during the procedure, so please also describe what actually occurred.

Response 2: We agree that bleeding could potentially be seen around the stent in a case of renal parenchymal injury like this. However, no signs of abnormal bleeding were seen intra-operatively. The kidney produced urine once re-perfused and no alarming bleeding was observed during the ureteroneocystostomy. There was hematuria seen post-operatively, which was initially attributed to the nature of the ureteroneocystostomy. However, the worsening hematuria prompted concerns which is why imaging was obtained. This thought-provoking comment was addressed with the following two edits. "A stent measuring 6 French by 12 centimeter (cm) was incorporated at the time of ureteroneocystostomy with no signs of bleeding intra-operatively. Hematuria was observed post-operatively..." (page 2, lines 46-47) and "The post-operative hematuria was initially attributed to the ureteroneocystostomy, but prompted concerns as the hematuria worsened." (page 7, lines 179-180).

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

I have read your paper with interest and found it to be clear and informative.

In my opinion, the case presentation (section 2) could be shortened, with some less important details removed. Additionally, this section should focus solely on presenting the events without including subjective statements. For instance, instead of saying, "We believe the additional guidewire and 195 stent manipulation with this method of placement increased the risk of injuring the renal parenchyma," you should present the facts without interpretation. Your opinions are perfect for Discussion section

Author Response

Reviewer 3,

Thank you for taking the time to provide feedback of the manuscript. The manuscript was edited accordingly and responses to your points are listed below. 

Comment 1: In my opinion, the case presentation (section 2) could be shortened, with some less important details removed. 

Response 1: We agree that the case report was long and could be reported more concisely. We aimed to reduce the length of the manuscript, while maintaining the relevant content and also addressing comments made by other reviewers. Your comments prompted a critical edit of the manuscript, resulting in reduction of the Case Presentation section from 917 words to 756 words. 

Comment 2: Additionally, this section should focus solely on presenting the events without including subjective statements.

Response 2: Thank you for this insightful feedback. During the edit of the manuscript, we took this into account and attempted to keep only objective information in the Case Presentation section and leaving interpretation for the Discussion section. The example you provided is now in the Discussion section (page 4, lines 11-12), along with other points of interpretation/opinions.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for revising the paper. It has clarified the serious events caused by the rare complication of renal parenchymal perforation by ureteral stent and the importance of managing them.

Reviewer 3 Report

Comments and Suggestions for Authors

The paper has been improved and can be accepted in my opinion