Surgical Anatomy of Urinary Segments and Operative Surgical Aspects




(1)
Urology Department, University of Turin, Turin, Italy

 



In the urinary tract the true segments are identifiable in renal lobes, in supernumerary kidneys, and, in theory, in complete or incomplete reno-ureteric duplicity (multiplicity). Those structures correspond to the previously described segment concept: They have proper functional autonomy and proper vascularization and innervation, and their removal, correctly executed, leaves the rest of the apparatus unscathed.

Even if one segment is removed (lobectomy) the portion of the kidney that is saved (the parenchyma and calyco-pyelic excretory system), is left normal and healthy (Figs. 7.1, 7.2, and 7.3).

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Figure 7.1
Outline of lower pole lobectomy


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Figure 7.2
Outline of lower pole lobectomy: open lower pole


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Figure 7.3
Outline of upper pole bilobectomy, showing the result


7.1 Renal Segments, Calycectomy, Segmentectomy, Lobectomy


As described earlier, the kidney is organized on a calyx that causes it to differentiate into secreting parenchyma once it reaches the metanephrogenic cup. Those tubules keep extending until they join the Bellini collecting ducts of calyceal derivation, of which they are a continuation. The minor calyx with its tributary pyramid and the surrounded cortex make up the renal lobe. From outside, with the exception of fetal lobature persistence (Fig. 7.8), lobes are not visible and hence not identifiable. However, penetrating the renal hilum and following the major and minor calyces it is easy to reach the renal papilla or pyramid apex through the loose connective tissue of the renal sinus. Having done this, through a small targeted nephrotomy, it is not difficult to identify the lobe and remove it correctly, by following each side of the pyramid edges inside the cortical tissue that divides one pyramid from the next (Figs. 7.4, 7.5, 7.6, and 7.7). Hemostasis occurs little by little as meeting vessels branch from the interlobar vessels and penetrate the pyramidal parenchyma and the vessels of the small interposed cortical tissue near the capsule. When and if the vessel’s small mouths are identified, clamping with a mosquito clamp is suitable and not difficult. This is followed by ligature or suture. For local, pathologic situations a severe hemorrhage could occur. It is better to clamp the renal artery or its tributary branch for that part of the kidney earlier. The clamping could be associated with renal cooling. In cases of surgical complexity, large areas of inflammation, or sclerosis, one could expect the ischemia to last more than 20 min. Whatever method one chooses, renal cooling must be performed to maintain the medullary at a temperature of about 20 °C.

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Figure 7.4
Lower pole lobectomy


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Figure 7.5
Lower pole lobectomy with open lower pole


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Figure 7.6
Upper pole nephrotomy to preparation of calyces


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Figure 7.7
Upper pole lobectomy

In cases of ischemic surgery, slow declamping promotes the vision of the bleeding source and a consequently easier hemostasis. However, clamping and declamping repeatedly is strongly to be avoided so as not to subject the kidney to subsequent reperfusion injury. The reperfusion is more dangerous than the ischemia on the renal parenchyma.

A hemostatic sponge can be placed between the surfaces, which must be approached and joined together through a continued capsular or interrupted suture.

This is the surgical outline of lobectomy or calycectomy, or renal segmentectomy. So it is clear that an important step in this type of surgery is the renal sinus opening to enter the kidney. This in fact constitutes intrarenal surgery.


7.2 Renal Sinus Access


Whenever one or more lobes are to be taken away it is critical that the renal sinus is accessed correctly. The morphology and amplitude of the renal sinus varies from individual to individual. As classically described by Henle (1866), the renal sinus is a cavity, isolated from the retroperitoneum, closed in practice and roughly rectangular in shape (5 cm high, 3 cm wide, and 2 cm deep), back to front. It is provided with two prolongations, one superior and the other inferior, which contain the major calyces.

The renal capsule is inside the sinus, in a certain sense papering the walls, thinning, and continuing with the calyceal adventitia. In this way each prolongation is lined by the kidney’s internal sheet of fibrous capsule. The size and morphology of the sinus are quite variable. The cavity occupies the space from the medullar parenchyma as the external edge, and hilus as the internal edge. The hilar size and shape are also quite variable. They can be small, large, semicircular, fessuriform, even punctiform, in renal malformations. Obviously the larger the hilum is, the easier access proves to be. Its anterior lip is less expanded than the rear one, which is protruding more medially. The sinus is elastic thanks to fatty tissue that is rather abundant surround the pelvis, calyces, vessels, and nerves. The elasticity allows them to expand and retract according to their function, filling, emptying, or contracting the pelvis and calyces, and contracting or relaxing vessels. Relaxation and contraction obviously occur according to the normal or the pathological processes within the sinus cavity.

The renal capsule reaches the extrarenal pelvis and extends a thin layer of dense fibers like a sheet, which surround and adhere to the extrarenal pelvis. This sheet, already mentioned by Disse (1891) as a capsular diaphragm, totally encloses the sinus, isolating it from the retroperitoneum (Fig. 7.8). In sinusal fat there are some stringy filaments running from the outside of blood vessels to the pelvis, as well as the major and minor calyces. In agreement with Gil-Vernet (1984), in kidneys with sinusal sclerolipomatosis it is possible to isolate sinusal structures without damaging them, thanks to the capsular coating that divides them from the nearby sclerotic tissue.

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Figure 7.8
Disse enclosure of the renal sinus

Access to the normal renal sinus is quite easy (Figs 7.9 and 7.10). The surgical steps are as follows: (1) Blunt separation and traction towards the parenchyma of the peripyelic fat, starting at the uretero-pyelic level and proceeding up from there. In this way the pyelic adventitia is left separated from the fat. (2) Putting the tip of a blunt pair of scissors, kept closed, below the capsular diaphragm, closing the pyelic adventitia then sharply opening it in order to achieve a generally rare capsular resistance. (3) Open the sinus entrance and once inside the sinus, an ad hoc handled retractor is placed, retaining the whole mass of peripyelic fat, capsule, the internal lip of the posterior renal edge, and the retropyelic vessels. The access is from the renal posterior face and it is easy to retract the block of tissue upwards without damaging or tearing the parenchyma, since, protected by a capsule and by usually dense peripyelic fat, it has great resistance and elasticity. The endosinusal structures are now visible. (4) By pushing gently, as deep as possible, an open wet gauze completes the dissection without bleeding. (5) In the posterior access, once the gauze is removed, the parenchymal lip is pulled with a second retractor, which closes the sinus.

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Figure 7.9
How to enter the renal sinus (according to G. Vernet)


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Figure 7.10
Pulling up the posterior polar lip facilitates the view of the minor calyx (according to G. Vernet)

The same process is followed for anterior access: the sinus concavity is more pronounced and open given the lateral rim retraction compared to the posterior one. For that reason, only considering the sinus entrance, access seems more facilitated, but to identify the pelvis and calyces it is necessary to separate the vessels, artery/ies and vein/s, from the pelvis. This represents a delicate surgical moment and a consequent risk, since the vessels must be moved from the pyelo-calyceal structures. For that reason the posterior side is generally chosen.

The aforementioned procedure assumes that the sinus is in a normal state. Stones, particularly those in the mould or staghorns, many types of inflammation, and malformative pathologies could greatly alter the hilum and sinus anatomy through a perirenal, peripyelic, and endorenal reaction, which is sometimes very severe, creating a more complicated, though not impossible, sinus access.

The author is in complete agreement with Gill-Vernet’s description: “…the most advisable procedure is to identify the most superior and free part of the ureter and from there follow a retrograde dissection with blunt-end scissors through the sclerolipomatous mass following a detachment plan which is always present between the pyelic adventitia and the peripyelitis. It is advisable to free the posterior surface of the pelvis from the sclerosed shell that enwraps it.”

Commonly, the innersinusal sclero-lipomatosis is less intense than the outersinusal one and that of the peripyelo-ureteric varices. This forms the basis for a guide to the surgical technique that starts far from the hilum, distally, at the level of a normal ureter and well distal to the sclerolipomatosis, where there is no pyelo-ureteritis.

The important thing to note in surgery of this kind is never to leave the adventitial plane of the ureter and pelvis. Into this plane place the tip of a closed blunt pair of scissors and push it gently upwards, close to the adventitia until it reaches the peripyelitis, i.e. sclerosis and sclerolipomatosis. There is always a thin space between the adventitia and fat sclerosis. With great care and patience continue to push the closed scissors as far as possible. The fat must be cut and opened but not removed, since the presence of the fat in the peripyelic vessels is usually not visible due to the sclerosis. The scissors should now be between the peripyelic fat and the pyelic adventitia, where there is always a plane along which one can run the blunt scissors. This is a guideline that must always be borne in mind (Figs. 7.11, 7.12, 7.13, and 7.14).

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Figure 7.11
In difficult conditions, like pyelo-calycal sclerolipomatosis, it is always possible to enter the sinus since there is a space between the excretory ducts adventitia and the sclerotic tissue. Under normal conditions it is usual to start from the ureter (according to G. Vernet)


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Figure 7.12
How to reach the sinus


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Figure 7.13
A gentle push with a blunt-closed pair of scissors creates a space between sclerotic and normal tissue. A small cut on the pathologic area and vigorous opening of the scissors amplify the space (according to G. Vernet)


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Figure 7.14
A gentle push with a wet gauze or a sponge promotes entry into the deep sinus at the level of the calyco-pyramidal junction (according to G. Vernet)

According to the amplitude and shape of the pyelo-ureteric junction, of the pelvis, and of their inflammatory coverage, it could be necessary to open the sclerosis with a little cut, which will gradually set the ureter and the pelvis free. It is extremely important to leave the adventitia sound.

The fat must be opened and accurately dissected from the pelvis, but not removed, since it covers peripyelic vessels, often not visible because of the thickness of the multiple sclerosis. Liberation of the intrasinusal structures will result in an emergency situation in the major calyces. Careful dissection will facilitate prudent freeing of all tougher fat and renal parenchyma. Once the major calyx has been visualized, a more vigorous freeing of sclerotic tissue and the sinusal parenchyma covering it will isolate the minor calyces without producing any harm. Deep gentle pushing of a soaked gauze will help isolate the intrarenal structures between the adventitia and reactive tissue, and reveal the minor calyx without creating damage.

The next part of the operation will be done accord to the lesions present.


7.3 Pathologic Situations Potentially Requiring Endosinusal Access


Undoubtedly the conditions that could necessitate endosinusal access to the intrarenal collecting system are not frequent occurrences. They include calyx or pyelic substance loss, their stenosis, malformations (such cysts, diverticula), localized and removable neoplasms, vascular pathologies interfering with calyco-pyelic dynamics, and the presence of stones that, due to their shape and dimensions need intrarenal surgery. Consequenty, pyelo-calycolithotomies, calyceal resections, end-to-end calyceal sutures, calycoplastics, calycopyeloplastics, bipolar calycocalycostomies, pyelocalycoplastics, and capsulopyeloplastics represent surgical techniques capable of curing or treating those pathologic conditions that utilize wide access to the renal sinus after hilum dissection.

Among those techniques that require ample opening of the renal sinus, one is of particular interest for the topic we are discussing: segmental resection or renal segmentectomy.


7.4 Renal Segmental Resection (Lobectomy, Calycectomy, Segmentectomy)


Renal segmental resection, also known as a calycectomy or, rather, a calyx-based resection, is the removal of a renal lobe (lobectomy) individualized through a minor calyx. It includes the pyramid apex, which is surrounded by cortical tissue like a cup. As mentioned in the introduction, with this kind of resection the residual parenchyma, in which the removed lobe (or lobes) had its natural parenchymal, vascular, and nervous individuality, is left sound.

Typical indications for this type of operation include pyelo-calyceal stones together with the resulting regional complication of pyelonephritis localized in one or more lobes, due to minor or medium calculolytic calyx clogging. In such cases simple stone removal allows for stone relapses in the very diseased parenchyma. However, segmental resection in such circumstances abolishes the cause of the disease, the stone, the effects of this on the parenchyma, the pyelonephritis, and the basis for stone recurrence, leaving the residual parenchyma completely sound and healthy.

In case of persistent surgical indications, the same can be said for hydronephrosis that is localized in one area and caused by an obstruction of a calyx tributary in a part of the hydronephrotic parenchyma, which is not further reparable and is caused by the calyceal obstruction, while the remainder of the kidney is normal.

Another example could be pyelocalyceal stenosis amendable with calycopyeloplastics. In this instance (Figs. 7.15, 7.16, 7.17, 7.18, 7.19, and 7.20) the inferior small calyx restores the normality of the pyelic cavity. The calyx is isolated at a polar level, detached from the apex papillae, opened, spatulated, and overturned on the breach of the pelvis and opened beyond the stenosis narrowing. The ablation of the lobe without its own calyx is not a true privation of normal tissue, since the stenosis certainly had an effect on the parenchyma, as hydronephrosis is to be expected after a calyceal stenosis. Thus a lobectomy following calycopyeloplastic surgery is curative in every sense.

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Figure 7.15
Calico-pyeloplastic surgery: the pelvis stricture is resolved through a wide pyelo-calical incision (personal technique)


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Figure 7.16
Calico-pyeloplastic surgery: calyceal preparation and dissection of the calyx


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Figure 7.17
Calico-pyeloplastic surgery: calico-pyramid amputation and calyceal spatulation


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Figure 7.18
Calico-pyeloplastic surgery: overturning of the spatulated calyceal flap


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Figure 7.19
Calico-pyeloplastic surgery: adjusting and suturing the calical flap on the opened pelvis and tributary parenchymal resection


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Figure 7.20
Calico-pyeloplastic surgery: removing the damaged, hydronephrotic lobe through a typical lobectomy

These are examples of infrequent pathologic conditions. As has been mentioned several times, the indications for renal segmentectomies are quite rare because the pathologies that potentially require that kind of surgery are rare themselves. However, rare does not means non-existent!

When there is an indication for surgery, the technique, despite its rarity, allows you to save the kidney and to occasionally treat very severe conditions.

Below is a descriptions of a typical inferior calycectomy or lobectomy.

In open surgery, the kidney is reached via an oblique, anterior access, such as a Fey incision. The peritoneum is detached using a smooth, blunt dissection from the Gerota fascia. After that a deep dissection will reach the ureter, which will be freed as far as the pelvis, once the renal lodge has been opened. The kidney is isolated from the anterior and posterior fasciae and the posterior surface is exposed. The renal sinus is freed from the Disse capsular closure, thus opening the sinus entrance. As described above, once inside the sinus, the major calyces are identified thanks to the delicate traction of the parenchyma and endorenal fat: a small nephrotomy is done in the direction of the small calyx that needs to be reached. The traction on the lips of the cut parenchyma produces the hemostasis of the ordinarily unimportant bleeding. The minor calyx is followed until it reaches the apex papillae. The anatomic situation will guide the progressive parenchymal cut so far that it will be possible to follow the anterior, posterior, and lateral edges of the desired lobe we have identified through a gentle traction on the calyx (Figs. 7.4, 7.5, 7.6, and 7.7).

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Feb 9, 2018 | Posted by in Uncategorized | Comments Off on Surgical Anatomy of Urinary Segments and Operative Surgical Aspects
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